Hello @Schifter, Gabriela,
The prompt for MFA registration is coming up because of Mandatory MFA enforcement by Microsoft on admin portal logins. In this scenario whenever any user is trying to login into any admin portal they will be prompted for MFA completion or registration if they have not already registered for MFA.
Mandatory MFA isn't configurable. It's implemented separately from any access policies configured in the tenant.
Unfortunately, there is no exception to this enforcement as the changes have been applied globally.
Kindly refer the below documents for detailed information on the enforcement as well as related FAQs.
Mandatory-multifactor-authentication.
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