couple of cheks.
Tools->Options->status->Show me DND when present desktop is checked ?
Reset the status on the client by clicking the drop down
Delete local cache files on client computer and login again
%userprofile%\AppData\Local\Microsoft\Office\15.0\Lync\sip_UserName@Domain.com
Registry Key: HKCU\Software\Microsoft\Office\15.0\Lync\UserName@Domain.com
Update the client to the latest version and give it a try.
Linus
