Authenticator app log in

When you install authenticator on a new device, it must be authorized for each account first, before it can be used. You typically authorize via alternative authentication (say the old device). If you do not have an alternative method then you will need to do an account reset (forgot password flow) for each account.

in the case of a Microsoft account you need to do the automated reset flow, which requires you to prove your identity. After identity approval there is a waiting period before reset. Due to security no Microsoft employee has access to your account.