Thanks for reaching out!
The error code AADSTS90072 is due to the external account that the user signs in with doesn't exist on the tenant that they signed into; so the user can't satisfy the MFA requirements for the tenant. The account must be added as an external user in the tenant first. Sign out and sign in with a different Microsoft Entra user account.
To resolve the issue, check if the user account exists in Azure AD Tenant. If the user doesn’t exist in the tenant, add them to your Azure AD. If the user is present, check if the invitation is accepted; If not, ask the user to accept the invitation.
You can also refer this link to see if it can solve the problem for you: - https://windowsreport.com/aadsts90072/
Hope this helps. Do let us know if you any further queries.
Thanks,
Akhilesh.
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