Lync phone doesn't ring, it just beeps a single time.

Hello everyone,

We are running into an issue where some of our users Lync Phones (Polycom CX600) are only doing a single beep when someone calls. The users phone will be working properly up until a random point and then it will only beep on incoming calls from that point forward. We have tried checking all the settings, resetting the Lync phone, replacing the Lync phone. Nothing seems to work. We are using Lync 2013 + 2010, and Windows 7.

Any help with where to look next would be appreciated.

Thanks,

Cory