AA Direct routing - 404 Not Found

I have seen so many entries in different forums with no actual fix, so hopefully adding this helps someone else. 

In this case, I replicated and E.164 format was the issue. 

We could see this in SIP trace.  The FROM number was always formatted properly but the TO was not ( even when coming from Teams client).   

• When you were calling a number to a user - this didn't matter, Teams seemed to normalize this internally and connected the call.
• When you called a resource account number- this would fail and Teams would return a 404 Unassigned number. 

We had to add inbound manipulation (Audio Codes) for our resource account numbers to add +1 so it was a proper E.164 Number.  This worked immediately.