Can't sign in through Microsoft Authenticator app

I have both a Work & School and Personal account registered with the same email address.

When I try to sign in with the Work & School account, I am told I need to supply more information and are then presented with a screen telling me I need to download the Microsoft Authenticator app to scan a QR code.

I don't have a phone that supports this app (I have a Windows phone).

There are no other options such as authenticating via email or SMS, so I am left unable to login.

Presumably I need to enable two factor authentication, but I can't sign in in order to do this.

How can I get around this restriction in order to sign in to my account?

Any help much appreciated...