As title states, voicemail is no longer working. We can somewhat determine that this stopped working after applying some updates to the lync server however it seems unlikely that rolling back updates (even if we knew which ones) would be a good solution. As there isnt a flood of people having these issues, I am leaning towards a configuration issue.
On the lync server itself, there is the following log that aligns to when people try and leave or check voicemail.
The URL it is trying to contact "looks" right.
Log Name: Lync Server
Source: LS Exchange Unified Messaging Routing
Event ID: 44009
Attempts to route to servers in an Exchange UM Dialplan failed
No server in the dialplan [Hosted__exap.um.outlook.com__<<ourdomain>>.com] accepted the call with id [1c7a6a9a-ea4b-4313-a843-56f3fba49252].
Cause: Dialplan is not configured properly.
Resolution:
Check the configuration of the dialplan on Exchange UM Servers.
Identity : Global
Description : Hosted voicemail policy for mydomain.
Destination : exap.um.outlook.com
Organization : <<ourdomain>>.com
Your help is greatly appreciated!