Insta password ok but still asking for backup or auth code

Hello folks, I logged in today and for some reason I can't access one of my accounts. I reset the password already (via email link). No problem. But on trying to log in now, it's still requiring either authentication app or backup code. I don't appear ot have either. I can still login to my main insta account. Any advice as to why it won't just accept the password and is requiring backup codes please? Any way I can get around this or am I done for?

The secondary insta account doesn't have a photo of me on it so I can 't confirm by video.

Thank you

Windows / Firefox 108.0