Before we get started:
When experiencing difficulties, always open a new “private” (Edge) or “incognito” (Chrome) browser window. This will avoid conflicting with other accounts and failed sign-in methods.
This only works if you have previously added alternative authentication methods to your Micrsoft 365 account. Check your verification methods at https://aka.ms/mfasetup
When you don’t have access to your Authenticator, select to use other methods like SMS and email to access your Microsoft 365 account.
As shown in the picture below, choose “Sign in another way“. (The exact wording may change.)
You will be shown alternative methods to authenticate (or verify) your identity.
In this example, we selected “Text” which will send a code by SMS to your phone.
Enter the code from the text message and you will gain access to your account or service.