We resolved the error by removing the Skype4B
client EndPointConfiguration.cache file and restarting the client.
Sometimes this file is not automatically refreshed by the
system and when there are DNS infrastructure changes, users could be
negatively impacted in a few cases.
Procedure to resolve error:
1. Sign out of Skype
for Business
2. Click File Exit
3. Open File Explorer
4. Type in
C:\Users\<username>\AppData\Local\Microsoft\Office\15.0\Lync\sip_<username>@companydomain.com
5. Press Enter
6. Select File:
EndpointConfiguratation.cache and delete it.
7. Launch Skype for
Business client and sign in.
