
Hi @Edward Jarvis ,
To fix these issues, run the Site User Mismatch diagnostic by using a Microsoft 365 administrator account (Global Admin or SharePoint Admin).
Site user id mismatch:https://aka.ms/PillarSiteUserIDMismatch
When the diagnostic detects a user ID mismatch in the UserInfo list, it will offer to remove the old ID. After you accept and the old ID is removed, assign the new user account the appropriate permissions to the SharePoint site.
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