How set or reset your Multifactor Authentication.

Why?

One word: security! Passwords are easily hacked these days, so MFA makes it more difficult for someone to break into your account. It adds an extra step to your login procedure, which confirms your identity.

You can also use this procedure to reset your MFA when, for example, you change to a new mobile phone or you have had to reinstall the Multifactor Authenticator app.

HOW:

Using an Internet browser (preferably Chrome or Edge), go to the O365 portal. http://office.showtex.com or Log-in | Microsoft 365 (office.com)
At the top right of the window, click on your photo or initials and choose “View account”
Now go to “Security info” and add a method. Optionally, you can remove old methods first.
Choose “Authenticator app”.
Now follow the setup procedure. Remember to first install the Multifactor Authenticator app on your mobile phone.
If the procedure is completed it is listed under Authentication methods.
Set this method as the default sign-in method. This is an ESSENTIAL STEP for Remote Desktop Logins

It is wise to add more authenticator methods but keep the Microsoft Authenticator app as the default.

Hopefully, this procedure will help to move on.