Hi @MUSYOKA KILONZO ,
I understand that your users are trying to register for MFA but receiving the following error:
We're sorry, we ran into a problem. Please select "Next" to try again.
If you check the Azure AD audit logs for MFA / Authentication methods , you should be able to get more details about the error and get a better understanding of why the registration is failing.
For example, the particular error you described could be connected to a Status Code such as, "User failed to start the registration for Authenticator App with Notification and Code."
This can happen if the user is not assigned the Azure Multi-Factor Authentication license plan and if there's something preventing the plan from getting assigned. If this is the case, you can go to Azure Active Directory > Select the user > go to License Plans > and check if either the license plan is not assigned or you are seeing an error preventing the plan from being assigned.
Alternatively, it can be that user just tried many times during short period of time, or that the account was flagged for a particular reason. Microsoft may limit repeated authentication attempts that are perform by the same user in a short period of time. You can try waiting a few minutes and trying with the Authenticator app or verification code (since the limit shouldn't apply to the Authenticator app).
Sometimes this can happen if there is an issue with the phone provider, or if the user's UPN changed.
If you have verified all of these causes but are still receiving the error, please feel free to reach out to me at AzCommunity@microsoft.com ("Attn: Marilee Turscak") and include your subscription ID and a link to this thread, and I will open a one-time free support case to help troubleshoot this issue.
If the information was helpful to you, please Accept the answer. This will help us and improve discoverability for others in the community who may be researching similar issues.