Hello @Daniel D ,
This looks to me like you already have configured MFA for that account, and that is why is asking you to use the App. Did you change your phone recently?
Is there any other Administrator in your tenant, that can help you with your account? The administrator can click "Require re-register MFA" for your account, which will ask you to register your phone app again. Or they can simply disable MFA for your account.
Please let us know if this helped.
Vukasin