When does the error occur?
The error occurs when you are trying to associate your TestComplete project’s test case with a test case 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 you have not specified any proper ID in the The ID of the Azure DevOps / TFS test case to add text box of the wizard.
Workarounds
Type the proper ID (it must be an integer value) in the The ID of the Azure DevOps / TFS test case to add text box or click the ellipsis button and select the needed test case in the Choose Test Case dialog. Then, click Add association.