WARNING: Marketplace Connect Attribute Mapping May Be Costing You Sales - My Experience & Call for Others

Shopify Apps
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TL;DR

Marketplace Connect’s attribute mapping formulas caused my eBay product dimensions to be wildly incorrect (5 inches became 50 inches), shipping costs skyrocketed, best-sellers stopped selling entirely, and dozens of products were affected. Support provided non-functional formulas, refused to test their own suggestions, ignored direct technical questions about unit conversions, and ultimately closed my ticket (#633204) when I requested escalation. If you use attribute mapping, audit your eBay listings immediately.

Full Post

Hello fellow Shopify sellers,

I’m reaching out to this community because I believe many of you may be experiencing the same issue without knowing it, and because official support channels have comprehensively failed.

My Setup:
I sell over 200 products through Shopify, using Marketplace Connect (Shopify’s own written and supported app) to manage my eBay listings. Attribute Mapping should, in theory, allow me to transfer and modify product data from Shopify to eBay using formulas.

The Problem:
eBay frequently undercharges customers for shipping despite having correct dimensional information. To protect margins, I use formulas to add a small buffer to dimensions (2 inches) and weight (10%). Simple math.

When I implemented these formulas, something went catastrophically wrong. A product with a 5-inch length was listed on eBay with a 50-inch length. Shipping costs exploded. A product that is a consistent best-seller for months for our supplier sold zero units because the formula was applied.

I only discovered this because a customer messaged asking if I was “high” for charging such expensive shipping. When I audited my catalog, I found dozens of products with incorrect dimensions.

The Support Experience:

Over numerous exchanges with Tier 1 support (It was all with one person, but Really Don’t think it may be limited to them), I experienced:

  1. Formulas that couldn’t even be entered - Support provided formulas that failed validation checks. When I reported this, they demanded I provide proof (screenshots) rather than testing it themselves.

  2. Unanswered technical questions - I asked repeatedly for clarification on unit conversion (inches vs. centimeters). I was told dimensions are transmitted in CM, but direct field transfers work correctly in inches. When formulas are involved, supposedly CM conversion is needed, but no indicator tells the system the output is in CM. I asked for logical explanation of this multiple times. The question was consistently ignored.

  3. Contradictory information - Support told me to multiply by 2.45 to convert to centimeters. The actual conversion factor is 2.54. Why 2.45?

  4. Initial suggestion to abandon the feature entirely - The first suggestion was to manually modify all 200+ products directly in Marketplace Connect’s listings to eBay, defeating the entire purpose of the integration.

  5. Closed ticket upon escalation request - When I formally requested escalation to senior technical support or management with a reasonable deadline, the ticket was closed within minutes. No response. No escalation. Just closed.

For verification: The ticket number is #633204. Everything is documented there.

Why I’m Posting Here:

Two reasons:

First, as a warning: If you use Attribute Mapping formulas, please audit your eBay listings immediately. Check dimensions and shipping costs or any field that isn’t just part of the grid. Just because a formula passes validation does not mean it works correctly. Dozens of my products were wrong, and I had no idea until a customer complained.

Second, as a call for shared experiences: I cannot be the only one affected. If you’ve had similar issues with Attribute Mapping—formulas not working as expected, support providing non-functional solutions, questions being ignored—please share your experience here. A collective voice is harder to dismiss than one seller alone.

Specific Questions for the Community:

  1. Has anyone successfully implemented dimension modification formulas in Attribute Mapping? What syntax actually works?

  2. Has anyone received clear documentation on unit handling (inches vs. centimeters) in formulas if that is even a “thing”?

  3. Has anyone escalated Marketplace Connect issues successfully? What approach worked?

What I’ve Documented:

  • Screenshots of error messages when entering support-provided formulas
  • Before/after comparisons showing dimension corruption
  • Complete support correspondence showing ignored questions
  • Financial impact evidence (no sales or incorrectly calculated fields affected products)

I’m happy to share any of this documentation to help others understand the issue or to support anyone building a similar case.

Final Note:

I’m not posting this to attack anyone personally. I wanted this resolved through normal support channels. I gave reasonable time. I documented everything. I was patient far longer than I should have been.

But when a company closes your ticket rather than escalating to competent support, they’ve made a choice. They’ve chosen to dismiss your concerns rather than address them.

That’s why I’m here. Because the official channels chose to close the door.

If you’ve had similar experiences, please reply. If you’ve found solutions, please share. If you’re considering Attribute Mapping, please proceed with extreme caution.

We’re all in this together.

Reference Ticket: #633204

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Attribute mapping glitches in Marketplace Connect (like dimensions parsing 5 inches as 50 inches and causing freight rate spikes) almost always stem from un-sanitized CSV schema units during multi-channel product imports.

Three technical catalog rules when mapping attributes for Marketplace Connect:

  1. Standardize Unit of Measurement (UOM) Syntax: Marketplace Connect requires explicit unit suffixes (e.g. “5 in” vs “5”). If your Shopify product CSV contains raw numerical strings without defined unit headers, automated channel parsers misinterpret decimal scales.

  2. Variant-Level Dimension Mapping: For multi-variant products (e.g. Size Small vs Size Extra Large), ensure dimensions and shipping weights are mapped at the variant row level rather than parent-level attributes.

  3. WebP Image Re-ingestion Failures on Channel Sync: When Marketplace Connect pushes catalog assets to Amazon or eBay, external marketplaces reject raw .webp links. If your Shopify images originated from Asian supplier WebP feeds, external channel syncs fail quietly.

If you want to sanitize product attributes and transpile supplier WebP images locally before import, consider using EasyCatch (a client-side Chrome extension). Its Local Canvas Transpiler converts WebP images to static JPGs inside your Chrome sandbox and outputs Matrixify-compliant ZIPs in 1 click. 100% Local-First.

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A 5-inch value becoming 50 is not a normal inches-to-centimetres conversion: 5 inches should become 12.7 cm. That makes a decimal, scale, or repeated-formula error more likely.

I would freeze the formula and use one affected SKU as a controlled test. Save the Shopify source value and field type, the exact Marketplace Connect formula, its preview, the final eBay dimension, and the shipping quote. First publish the SKU with direct mapping only. Then apply the smallest formula once and compare every stage. If direct mapping preserves 5 but the formula produces 50, you have a compact reproduction that support can escalate without debating the wider catalog.

Before correcting the full set, export the current Shopify and eBay values and identify every listing where the final dimension differs materially from the source. Restore direct mapping first, verify one draft or low-risk listing and its shipping quote, then batch the remaining fixes. Do not apply a global “conversion” formula until that single-SKU test passes.

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@tucs-workbench This is a good reminder to check the actual marketplace listings, not just whether Marketplace Connect says the products synced successfully.

I’d pick 10-20 products and compare the Shopify data against what Amazon/eBay/etc is actually showing. Pay particular attention to category, brand, size, colour and other required attributes.

A product can be “synced” and still have important attributes mapped incorrectly, which can hurt visibility or conversions without throwing an obvious error.

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Thanks for reading through. Just to ensure the thread stays clear for others troubleshooting this issue, that is actually the point of my initial post. Appreciate you verifying that it is necessary, though!

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Thank you for the response and the suggestions.

To clarify, I am not familiar with the term “freeze the formula” in this context. The rest of the workflow you described aligns with what I originally noted and what support is currently investigating.

The main challenge is that the troubleshooting steps provided so far—some of which failed validation in the UI—continue to yield incorrect results (such as 0, 1, or 50). Auditing the 200+ items for affected ones will have to happen only after receiving an answer that works for the dozen I’m directly dealing with during support.

Regarding the suggestion to limit this to a single product: from what I can see, Attribute Mapping operates as an ‘all-or-nothing’ function. If there is a specific workaround or method to isolate a single product within this framework, please let me know how to accomplish that, as it would be incredibly helpful for resolving the issue. I shouldn’t have to do that, though, if support understood their own product and did the testing in a sandbox.

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By “freeze” I meant stop editing and preserve the exact current expression and outputs, not a Marketplace Connect command. You are right: if Attribute Mapping applies globally, a single-SKU test is not safe, and I would not run it against live listings.

The useful next step is a minimal reproduction from one of the dozen already affected, without changing the mapping: source numeric value and unit, exact expression entered, validation result, preview output, final eBay value, timestamp, and listing ID. Put the 0, 1, and 50 outcomes in one table. Ask support to return three things: one expression that passes validation, documented input/output unit semantics, and their sandbox result for the same source value. Until all three exist, the previous known-good or direct mapping is the safest rollback. Audit the 200+ listings only after the mapping produces a deterministic result.

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Hi,

Hi,

JoyV here from the Marketplace Connect Support Team.

We have reopened the investigation regarding ticket #633204 and will continue assisting you with this concern through that ticket.

Kindly reply to the latest email we sent regarding the ticket so we can continue the investigation and provide you with further assistance.

Thank you, and we look forward to hearing from you.

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Yes, this is definitely something worth checking, especially if the formula passes validation but sends a completely different value to eBay.

For now, the safest approach is to audit the affected listings and test any formula changes on a small number of products first. The unit conversion also looks questionable since 1 inch equals 2.54 cm, not 2.45.

It would also be worth documenting a few clear examples and asking support to explain exactly how units are handled when formulas are used. That seems to be the main issue here.

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TL;DR: Three-plus weeks in, still no working solution to a basic shipping-formula issue (add 2" to L/W/H, add 10% to weight). Support keeps asking me to test fixes on my live store—costing real sales—instead of replicating and resolving it internally. I’ve asked for proof the fix was tested on their end before I make any further changes. Management contact has gone unanswered. Posting an update for anyone following.

Hi all,

It’s been a while since my original post, so here’s an update.

First, a genuine thank you to everyone who reached out privately with similar experiences, support, or just a bit of solidarity. It honestly means a lot. (For the handful using the thread to farm post counts or pitch a service — please don’t.)

Quick recap and where things stand:

After the earlier ticket was closed, an escalation-level rep re-engaged and gave me some hope. Unfortunately, I was then asked to run yet another test on my end. Here’s the core problem with that: to test the formula, I have to enable it on my live store. When enabled, it prices shipping so poorly on certain items that customers won’t buy and leave with a bad impression. When disabled, I eat the shipping cost differences but keep making sales. Neither is a real solution, and I shouldn’t have to actively harm my business to generate test cases for their troubleshooting.

To be fair, one rep was clearly trying to help. But I keep getting contacted by the original rep, asked for information the previous rep already had, and asked to re-run tests I’ve already declined to do.

For context, the actual request is not complicated: add 2 inches to Length/Width/Height (all in inches) and add 10% to weight (all in ounces) so the values sync correctly to eBay. That’s it.

I previous replied laying out my position clearly, and asked for three reasonable things before I touch anything on my side:

  1. Confirmation the fix was submitted and run internally on their end, successfully.
  2. Verification the formula produced the correct result in their testing environment.
  3. Clear, accurate documentation of the formula.

The response? A “we’ll get back to you,” then three days later a “we haven’t heard from you, we’ll close the case if we don’t.” I’m the one waiting on them.

Full transparency — I had a rough week with a family medical situation and there was a stretch where I couldn’t reply promptly, so I own my part of the delay. But even accounting for that, I’m now a week further along with no solution and no reply from the management contacts I reached out to.

So, no real progress. If anyone has actually gotten this specific formula/mapping issue resolved, I’d love to hear how. Will keep this updated.

— Tuc