Lync Error ID 3110 (source ID 243)

In our implementation of Lync, we had users that would consistantly get an error 3110 when trying to join recurring meetings. troubleshooting revealed that the servers were originally deployed in default mode with Enterprise Voice enabled. We soon discovered that our network couldn't handle so much simultaneous real-time traffic, so we disabled enterprise voice for all but a small, select group of users. While we were troubleshooting, I found a workaround:

So, the workaround allowed users to enter the meetings, but it was not solving the issue. I spent a good deal of time troubleshooting this and I believe the root cause is the fact that we disabled EV for the vast majority of users. The meeting URI created when the users were initially created meant the meeting had audio rights, and since the user's didn't anymore, the join for the user was trying to open an audio session. Since the users didn't have audio conference rights, the join fails for audio, but you can see by the picture above, you are in the lobby. To join the meeting, all you have to do is click on IM and type something in. The true fix would be to either have the users cancel all preexisting recurring meetings, or set the meeting configs to force a new URI to be generated for each and every meeting as shown below:

That should make your 3110 errors a distant memory.