We use pidgin (2.10.2) with the sipe plugin (1.15.0) to connect to our Lync 2010 server. Until a couple weeks ago we were using sipe 1.13.x but kept having issues with users not becoming available after being idle.
Ever since we updated sipe to 1.15.0 (or the interim version 1.14.x) Pidgin clients have been occasionally showing users offline even when they are online. We have a mix of Windows Lync, Mac Lync and Linux pidgin/sipe clients (totaling at about 1300) connecting to the Lync server.
Disabling and re-enabling the sipe account (or restarting pidgin) sorts the issue for a while but the problem will come back. We noticed two different problems which may or may not be related:
1) Some users show up as being offline in the buddy list but I am able to send them messages which they will receive and they can reply too. This is confusing as users never know whether another user is actually online or offline.
2) User shows as online but trying to send him a message will result in Pidgin throwing the following error in the conversation window 'This message was not delivered to <username> because they are offline'. At this time he was online. The problem can be fixed by the user restarting his pidgin.
Have you seen these problems? I keep following the changelog but not seen anything related yet.