Hi!
Does anyone else have the same issue in your organization?
If you set your account in another computer, does the issue persist?
We recommend you check the following things to troubleshooting this issue:
*Verify if Server discovery is succeeding or not. Simpler way to identify if DNS Records are the problem is by testing Manual Sign in vs Automatic Sign in method.
*Verify if Network Connectivity is succeeding or not. We could make use of Telnet or Port Query tool (needs to be installed) to check if required ports are open(such as 5061,443) and whether client is able to make successful connection
*Check if there are any error event logs in the front end server.
For more details about how to troubleshooting Skype for Business Server sign-in issue, you can learn it from:
https://learn.microsoft.com/en-us/archive/blogs/praj/troubleshooting-skype-for-business-client-sign-in-issues
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