Does not seem uncommon?
There are several threads on this issue:
Thank you for that, i did try those steps in the registry when i was researching the problem
Now i still cannot join and i get an unknown error has ocurred, microsoft cloud services returned an error
I am experiencing the same problem on multiple WSE 2016 and WSE 2012 R2 systems. I cannot create a new connection to Microsoft Cloud Services (I just want Azure AD connect) on a new WSE 2016 Server. I also have multiple WSE Servers that were connected and syncing with Azure AD that now no longer connect or sync. Removing the Cloud Services connection and trying to reestablish simply refuses to complete and only returns a status of "An unknown error has ocurred." Removing the BecEndpointAddress registry key has no effect on this problem. I have run exhaustive Google searches on this and found almost nothing useful.
I have no solution. Apparently Microsoft does not either. Just confirming that this is a real problem yet to be repaired by Microsoft.
Open a case at Microsoft and tell them it must be fixed.