Make it optional! 2FA can get in the way and should be optional. As a developer I carry different phones, depending on which app I’m developing. The verification goes to the phone I’m not carrying today. And, my family gets locked out until I get the right phone and send them the code in a timely way. We left Sprint because accounting got the notifications but the folks trying to make changes (for which they were authorized) could not until the accounting folks got back from lunch or the next day. I would prefer a simple notification that changes were made. Make 2FA optional.