Hi there,
Thank you for reaching out to us!
We are trying to provide a reply and some information to older posts, in case others come across the same situation and it would help.
The flow that you are trying to achieve, of prompting the users for MFA after they have changed their password, can be accomplished and has been described in this following topic as well, with the use of the Password Reset Flow, which allows you change the behaviour between the time of the user completing the first challenge and before the new password is set.
Hope this helped!
Gerald