image and price don't change on variant change on product page

Topic summary

A Shopify store owner is experiencing an issue where product images and prices fail to update when selecting different variants on the product page. The problem occurs when using a sticky add-to-cart app.

Current Behavior:

  • Variant URL changes correctly when selections are made
  • Images and prices only display correctly after page refresh
  • The sticky add-to-cart widget itself shows correct information

Root Cause Analysis:

  • The app developer indicates the app updates the URL with the correct variant ID, but the theme isn’t updating its variant state accordingly
  • Potential code conflict between the app and theme code suggested

Technical Challenge:

  • User cannot locate a product.liquid file in their theme (uses product.json instead, indicating a newer Shopify 2.0 theme structure)
  • Attempted code modifications resulted in multiple errors
  • User is uncertain where to implement potential fixes

Status: Unresolved - user needs guidance on proper file location and implementation method for their theme architecture.

Summarized with AI on November 5. AI used: claude-sonnet-4-5-20250929.

Hello,

when I change my variant using my sticky add to cart app, nothing changes on the product page. The app says it is not happening because of the app since the variant url does change. Can someone please help me with this.

It does show the correct price and image after refreshing but it should display correctly on variant change.

In my app sticky add to cart widget the image and price change correctly. URL: MagCharge – TrendBlend

Well it means it is changing but changes are not live until page loads. This is a problem from the app.

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The app creators said this:

Were you able to read our previous email regarding the image on the sticky bar? I’ve noticed the issue, and it seems like the app updates the URL with the correct variant ID, but the theme isn’t updating the variant state.

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May be the app code clashes with some part of the theme code.

Hello, there is no product.liquid file, which file should I put the code in?

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Hello, there is no file such as ‘product.liquid’

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Hello, I do have a product.json file: Sep 30 4:18 PM - Codeshare.

But I’m not really sure where to add the code, it gave a lot of errors when a pasted it at the bottom of the file