Hello Steve
Welcome to Microsoft Q&A Platform, thanks for posting your query here.
Based on the information you provided, it seems like you have followed the correct steps to enable Azure AD authentication during the setup of the virtual machine and have enrolled yourself via the IAM. However, you are still getting an error message when trying to log in using Azure AD credentials.
-Ensure that the Azure AD extension is installed and running on the virtual machine.
Get-Service AADLoginForWindows
If the service is not running, you can start it by running the following command:
Start-Service AADLoginForWindows
Ensure that the virtual machine is joined to the correct Azure AD tenant.
Get-AzureADComputer
This should return information about the virtual machine, including the Azure AD tenant it is joined to.
Ensure that the user account you are trying to log in with is assigned the correct Azure AD role. To log in to a virtual machine using Azure AD credentials, the user must be assigned the Virtual Machine Administrator Login or Virtual Machine User Login role. You can check this by going to the Azure portal, selecting the virtual machine, and checking the Access control (IAM) settings.
Hope this helps.