Today my Lync mobility was broken. I simply could not connect to Lync on my mobile device. I was baffled because some users could connect.  A closer look revealed that users that were connected were most on a different Lync Pool. I enabled logging on my device and tried again and the I send myself the diagnostic logs from Android Device. Below is the clue to the problem preventing me from using Lync Mobile

This showed me that one of my front end servers was ailing. I immediately went for the event logs on the front end servers.

Upon checking event logs for clues, I was greeted by event id 1309

Solution

I could restart the server, but since this was just one IIS Application Pool , I decided to stop start and start the pool

In minutes the service was back up and running again.