Thanks for the post! If you receive a 400 error code when using TestRail’s API, you should also receive an error message with the request relating to the cause of the error.
Typical causes of a 400 error would be an invalid/missing header (All GET requests and non-attachment POST requests require the
Content-Type: application/json header) or an invalid project, case, or other entity ID.
Can you provide the response message provided by TestRail’s API along with the API method you are using so we can provide additional details?
If you’d prefer, please email a copy of the full API request and response to firstname.lastname@example.org so we can review the full request details.