Hello Christine Offner,
Thanks for your question.
The way to resolve this is to request for Product Support to reset MFA for the affected users. Contact Product Support with the email address for the affected user.
You can reach out to Global support: https://support.microsoft.com/en-us/topic/customer-service-phone-numbers-c0389ade-5640-e588-8b0e-28de8afeb3f2
You can mark it 'Accept Answer' and 'Upvote' if this helped you
Regards,
Abiola