Hi Tommy,
As per your error message, here I find one similar thread you may refer this thread and see the result.
As you mention “Additional security verification" is missing from his security settings” Administrators can also reset user's MFA through https://portal.azure.com Then selecting Azure Active Directory -> Users -> Select the User -> **Authentication Methods.**There you can set up some types of authentication methods, require them to re-register, and reset their password as well.
Here are some articles for your reference:
Enable Azure Multi-Factor Authentication.
If issue persist, then for Microsoft Authenticator with the two-factor authentication related issues and questions, we have a specific channel and we suggest you post a new thread in Microsoft Authenticator app forum for further expert help.
I appreciate your time and understanding.
Best Regards
Waqas Muhammad