We have actually dozens of Lync clients stopped working. We studied technet, google for similar cases and there are different.
Lync client can't log in at all. There is no error, event, prompt or so. We try with Lync 2013 [15.0.4641.1001] and Lync 2010.
What we checked:
- remove lync cert on clients,
- clean login data,
- set manual configuration and point to lyncpool.domain.com or lyncpool.domain.com:5061 or lyncpool.domain.local:5061
- Ping, tracert to lyncpool.domain.com and lyncpool.domain.local works fine.
- Load accapilog from %LOCALAPPDATA%\Microsoft\Office\15.0\Lync\Tracing\ in Snooper and no items in Messages tab
- Wireshark indicate no network traffic communication with lync server
- No items in Windows Credential Manager
- Ipconfig /flushdns & /renew done
- time&date is correct
- OCS & Lync Automatic Sing-In Troubleshooter display one DNS record _sipinternaltls._tcp.domain.com type SRV hostname lyncpool.domain.com Port 5061
- Reinstalling Lync, Office, with regedit clean not helped.
Some users report that when they connect by Wi-Fi it works.
What else can we check?