O365 3rd Party Application Login

We have a single user that is unable to login to a web application using their O365 credentials. All other users can login fine. I have checked the logs and it's getting this error message.

Eror: AADSTS50076 UserStrongAuthClientAuthNRequired - Due to a configuration change made by the admin, or because you moved to a new location, the user must use multi-factor authentication to access the resource. Retry with a new authorize request for the resource.

What does it mean by "Retry with a new authorize request?". They have MFA enabled through O365, I have disabled this and they can login successfully. Re-enabled and setup their MFA again and it comes back with the same error message in the O365 logs. Has anyone seen this error message before? Any help would be greatly appreciated.