Issue : Lync mobile client can not sign-in .
During my troubleshooting on my lync director server, I see Event 4101 which indicating “Certificate file path” can not be found. I tried to browse the File store asscitae with DIR servers and can not browse. So its confirm that problem is occurring due to store only. You can also see this event if you have permission problem on lync store directory.
Worked with Storage admin to enable the lyncShare directory with old data which resolved the issue.