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Understanding API 400 Errors and Sudden Integration Failures

If you use the WSM API to connect your store to backend systems, order management tools, or other services, you may occasionally run into errors. This article explains two common situations—a 400 error response and integrations that suddenly stop working—and how to resolve them.

Note: This article does not cover requesting an API key, plan eligibility, or general authentication (403) troubleshooting. Those topics are covered in separate articles.

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Understanding a 400 Error Response

A 400 error usually means the request was malformed or that the conditions of the request weren't met. In other words, the API received your request but couldn't process it as written.

Common causes include:

    • The request structure (XML) is incomplete or contains a formatting mistake.
    • Required parameters are missing or in an unexpected format.
    • The conditions for the request simply weren't met.

It May Not Be a Real Error

One important thing to know: a 400 response can sometimes look like a failure when it's actually an empty result. For example, if you call an endpoint to retrieve new orders and there are no new orders to return, the response can appear to be an error even though the request worked correctly.

What to do:

    • Review the request you sent for any formatting or missing-parameter issues.
    • Confirm whether the situation you're querying (such as new orders) actually has data to return.
    • If you're unsure whether the 400 reflects a real problem or just an empty result, contact support to confirm before assuming your integration is broken.
When API Calls Suddenly Stop Working

If your integration worked reliably and then suddenly began failing—with no changes on your side—the cause often points to something that changed on the WSM side rather than in your code.

Possible causes include:

    • Your account or plan changed.
    • A temporary platform issue occurred around that time.
What to do:
    • Check whether anything changed on your side first (even small updates).
    • Look for any known site or platform issues around the time the failures began before assuming your integration broke.
    • If nothing on your end explains it, contact support so we can investigate on the WSM side.
What to Include When Contacting Support

To help us resolve API issues quickly, please include the following details in your request:

    • The exact endpoint or action called (for example, the module and action in your request).
    • The error code and the full response body you received.
    • When it started failing (the approximate date and time).
Providing these details up front allows us to identify the cause faster and get your integration working again.