After seeing the Request to Allow/Deny the permission, if we click "Allow" we get this stack trace on visual studio online:
Web.Services.Tfs.AuthenticationException: Authentication failed. Error code: Unauthorized
at Web.Services.Tfs.TfsModule.<>c__DisplayClass53_0`1.<<TfsGet>b__0>d.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
at Web.Services.Tfs.TfsModule.<InvokeWithAuthRetry>d__55`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at Web.Services.Tfs.TfsModule.<InvokeWithAuthRetry>d__55`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()