Hi @John Rubin
To troubleshoot your issue, I have some questions to confirm with you:
1)Have you tried to change another account to see if it can be reproduced?
2)Do you have any operations before this issue occurred?
According to your description, it seems you are using Skype for Business online. In this way, we firstly recommend you ask your admin to help check them at first. Moreover, if convenient, please change to other networks outside your organization to check if it can make any difference. For more information, please refer to Troubleshooting Skype for Business Online DNS configuration issues in Office 365
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