To troubleshoot common single-client Lync issues, a good starting point is to clear the client cache.

Common Single-Client Errors

“Problem Acquiring a personal certificate that is required to sign in”

“Lync Server is temporarily unavailable”

“User is not SIP enabled”

“Lync cannot connect to the Exchange server. Please try signing out and signing back in.  Outlook Contact and calendar information will be unavailable until the connection is restored”

note, a common fix for this issue is to close Outlook and reset items within folder cache.  Close outlook, then run the following to launch Outlook again: outlook.exe / resetfolder

Contact hotos are missing or incorrect

Contact cards are out of date

Cannot search for user in Lync

 

Fix

Again, clearing the Microsoft Lync Cache is a good fix for issues affecting a single Windows client.  If a problem is persisting for several folks or throughout an organization, the fix is probably in server configs.

Close Lync completely (make sure to right click>exit from the system tray)

For Lync 2010, open <user profile>\AppData\Local\Microsoft\Communicator\

For Lync 2013, <user profile>\AppData\Local\Microsoft\Office\15.0\Lync\

delete the sip_username directory (it will be rebuilt at the next Lync launch)

Microsoft articles commonly identify single files to delete depending on the issue.  We have never seen an issue with deleting the entire directory.

Reset-MSFT-Lync-Client-Cache

 

We have been doing a lot of testing with the new Lync 2013 Microsoft products lately and have been impressed by results.  On-premises testing runs smoothly and Office 365 offerings run great in the cloud for SMBs.