Not receiving MFA requests from external 'Microsoft CRM Portals' - Error 500121 (all other apps ok)
Our users are not receiving Microsoft Authenticator codes when logging in to one specific external application 'Microsoft CRM Portals'. The alternative process, entering a code from the app, also fails with error 500121.
All other internal applications are accessible with the MFA codes generated by the same Microsoft Authenticator app, and are able to send push notifications to the app. I don't have any other external applications to test further if it's an issue with external applications or an application specific issue.
I'm unsure if it's relevant, but in the past this external tenant app sometimes required users to reset their password to mitigate 'risky user' status in Entra, but now it does not generate MFA requests at all. The users are not in 'risky user' status, however we have attempted self-reset anyway and this time it has not resolved the issue.
Any help is appreciated.