Microsoft Authenticator loop

Question

We've got a new employee who's account is replacing an employee who left, should be same licence.
I've managed to log her onto New Outlook using the Microsoft Authenicator. But she's only been able to access New Outlook not the normal Outlook and doesn't have the permissions to see the inboxes she should have. (The person with full admin access is legally blind and works from home, so something could be occuring there).

But we know the email is active because she is sending and receiving in New Outlook.

Trying to log her into the normal outlook on any device causes a request from Microsoft Authenticator.

Trying to add her account to Authenticator means it asks to be Verified by Authenticator. And we just go round in circles.

On the device she was orginally verified with it shows her as Microsoft Entra ID instead of the company name (which is what every other company email shows) and when I tap on it, it only shows connect account and set up 2-step verification.

I'm at a loss, any suggestion would be helpful.