A cloud-based identity and access management service for securing user authentication and resource access
Hello Craig Martin (Soben North America LLC),
Glad to know the issue is resolved and Excel is working fine now. Since this was related to a Microsoft internal tenant, contacting the MSIT support team was the right approach.
As discussed offline, please start with the chat option in the portal if you face this again. From there, the support team can assist further and create a support ticket if needed. You can access the portal here: https://aka.ms/msit and initiate the request via chat.
Thanks for confirming.