Why does my 'Add to Cart' button periodically give a 'Parameter Missing or Invalid' error?

Shopify Discussion

Topic summary

  • Issue: Intermittent “Parameter Missing or Invalid: Required parameter missing or invalid” when clicking Add to Cart. Happens mainly on first visit via a new tab or incognito mode; a page refresh makes it work. Affects all products. Theme: Spotlight. A screenshot is attached.

  • Impact: Risk of lost sales due to customers encountering errors before adding items to cart.

  • Preliminary diagnosis: A responder suspects the product form isn’t passing required parameters (e.g., quantity or variant) to the cart on initial load/new sessions. They inquire about any theme customizations that might affect form behavior.

  • Actions requested: Provide the store URL (and password if needed) for inspection. Check that the Add to Cart form reliably sends variant and quantity parameters, especially on first page load and in private/incognito sessions.

  • Status: Unresolved and ongoing; awaiting store details to reproduce and debug the issue.

Summarized with AI on January 17. AI used: gpt-5.
1

From time to time my add to cart button leads me this error called “Parameter Missing or Invalid: Requited Parameter Missing or invalid”. This error mostly occurs when I enter the site from a new tab or incognitio mode. Then after I refresh the page and try to add to cart again the problem doesn’t not occur. It doesn’t matter which product I try to add to cart. All of them produces the same error. This is a huge problem for the customers they won’t be having that kind of patience.

My theme is Spotlight.

Ekran görüntüsü 2023-09-20 183102.png
Ekran görüntüsü 2023-09-20 183102.png825×708 15.5 KB

2

Do you mind sharing your store URL (and password if necessary)? There may be an issue with the form pass information regarding the quantity or variant or something else. Has any customization been done?