To understand your problem in detail I have a few questions
- What is the intention of authentication? Are you trying to use the workbench API directly without the UI?
- How are you obtaining the token? Against a user who is a part of the AAD or a SPN?
Just of debugging can you open the workbench UI, go to the networks tab, open an XHR request to the API web app and copy the authorization token from the header and use it in your application? This would help us understand if the issue as to why your token is giving a 401 error?