Unfortunately, removing a security option like the Authenticator requires some steps. If your husband had SMS Protect set up on their account they could use that to help remove it, but it sounds like they may not have.
In that case, he’ll need to contact our Support staff to have it removed for him. He can start that process here:
He’ll enter his email address and then, instead of clicking the Text Message or Authenticator Code option click the blue box that says “Verify your account information”. A Game Master will get that ticket and likely send him some account specific questions.
He’ll want to open a new ticket (as outlined above), providing those answers as best as he can. Once those answers are verified our staff can remove the old Authenticator. Then you can set up the Mobile App and use that instead.