Hi @Thtgrldiana , You may have done this already, but please register or re-register the MSAUTH app as an authentication method here.
For deleting users, check to make sure that the user does not have their account enabled on the Account Security page or the MyApps page for work and school accounts.
Please let me know if this works or if you have any questions!
If this answer helped you please mark it as "Verified" so other users may reference it.
Thank you,
James