Hi desert lion 67,
What is your environment? Online or on-premises?
Do you mean that the error message is KB2566790?
If so, this issue is generally related to the Skype for Business DNS configuration with your Office 365 account. If your environment is online, you
can refer to this article to troubleshoot it:
https://docs.microsoft.com/en-us/SkypeForBusiness/troubleshoot/online-configuration/dns-configuration-issue.
If not, please give us a screenshot of your error message to know your situation clearly.
Best Regards,
Sharon Zhao
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