How do I reset authenticator app for 2FA?

[MJT74]

Hello. I currently have my primary 2FA access as an authenticator app - but I have several on my phone and none of them seem to work. I can still access my account if I 'Use a different method' and send a SMS. I don't want to do this in the long term as SMS is not as secure. Does anyone know how to change the 'primary device' so I can reset the authenticator app? Many thanks everyone!

[TECH-Ing]

Deactivate 2FA and reactivate.