Hello @Doug Hardy ,
After our discussion on this issue, we decided to submit a Microsoft support ticket to remove the user email ID which was previously registered with Azure Sphere Tenant. This will make sure that the user can register again with the Azure Sphere Tenant without any issues. We will make sure to capture this scenario as part of our Azure Sphere documentation. Thanks for your contribution to this forum.
We hope this info is useful to others as well with a similar situation.
Updated: 11/11/220 , Product-Bug
The old public Microsoft account needs to be removed everywhere so Graph API maps the email to the new AAD principal id. The Product team and support team investigated this & helped in removing the old account.
Microsoft Teams
Thank you,
Satish.
Azure CXP Team.
Redmond-WA, USA.