This was a fun little mess to troubleshoot and in the end the solution was quite unexpected and a little alarming (sigh)
Some time recently all incoming calls from external callers stopped notifying both the desktop and client Teams apps. This issue did not affect calls coming from Call Queues nor did it affect calls to Teams mobile apps. This was a serious head banging and hair pulling issue that affected every user in our organization. What the heck Teams?!
After much, much troubleshooting and even more online searching for similar reported scenarios no solution could be found… so reluctantly we had to open a support ticket with Microsoft 365 (sigh) The issue persisted and the support ticket remained open without resolution for over a month. Every now and again I would attempt to review the issue and hope to find something I’d missed in previous troubleshooting attempts. And then…BAM! I found the culprit.
The fix for the issue was quite alarming (head shaker) and I am convinced this is a “bug”.
Teams Voice – Caller ID Policy
If this is set to “Enabled” and you are experiencing the issue described in this post then “Disable” it and test if external calls to either Teams client or web apps start working.
This setting should NOT break incoming external calls. This setting is supposed to…
If Teams Admin portal will not allow you to save the policy after you disable the Caller ID setting (which was the case for me) then use PowerShell and it will work.
Set-CsCallingLineIdentity -Identity "MyBlockingPolicy" -BlockIncomingPstnCallerID $false