When does the error occur?
The error occurs when you are trying to associate a TestComplete 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?
TestComplete shows this message if it has failed to add the association between the test cases properly. This can happen, for example, if TestComplete is not able to connect to your team project.
Workarounds
Make sure that TestComplete can connect to your Azure DevOps or Team Foundation Server team project and access its test cases.