Hi @Glen Palmer , make sure that the devices are properly joined to Azure AD. Sometimes, devices might not be fully registered, causing authentication issues. You can verify this in the Azure AD portal under "Devices."
Double-check that your admin account has the necessary roles assigned in Azure AD. You should have roles like "Global Administrator" or "Intune Administrator" to perform administrative tasks.
When users log in with their M365 accounts, they might not have local admin rights on the device. You can configure this by adding the admin account to the local administrators group on the device. This can be done via Intune policies or manually.
Review any Conditional Access policies that might be affecting admin logins. Sometimes, these policies can inadvertently block or restrict admin access, and verify MFA is not causing issues with admin logins. Sometimes MFA prompts can interfere with the authentication process.
If you're using password hash synchronization, check that the passwords are correctly synced between on-premises AD and Azure AD.
Please let me know if you have any questions and I can help you further.
If this answer helps you please mark "Accept Answer" so other users can reference it.
Thank you,
James