@SJM4010 ,
Could you provide us a screenshot of the error message if possible?
Does this issue persist all the time? Or what changes do you do before this issue happened?
Does anyone else have the same issue?
It recommends the affected user try to log in other machine and observe if this error message still exists.
If it works properly, clear the client cache as below:
- Right click the Windows icon and open the Run bar
- Type in: %localappdata%\Microsoft\Office\1x.0\Lync\ folder
- Delete the sip profile folder.
- Go into the Tracing folder, delete all files.
Besides, remove related Windows credentials and try again.
If the problem still exists, it should relate to account itself. Contact the IT admin can check if there is special setting on the affected users.
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