When does the error occur?
The error occurs when you are trying to associate your TestComplete project’s test case with a test case, which is managed by Azure DevOps or Team Foundation Server, via the Associate with Azure DevOps / TFS Test Cases wizard.
Why is the message shown?
The message is shown because the ID you have specified in the The ID of the Azure DevOps / TFS test case to add text box corresponds to a work item that is not a test case. TestComplete test cases can be associated only with test cases.
Workarounds
Specify the ID of a work item which is a test case, or click the ellipsis button and select the needed test case from the Choose Test Case dialog.