[Defender] Two Factor Authentication not working

A couple of weeks ago, we installed Defender into our site https://newberyconsulting.com.au/. We love it. We enabled two factor authentication early and this has been working well. On about Wed this week, we were no longer been requested to enter the code from authenticator. For some reason it just stopped requesting the code on log-in for me and other users. I have checked both the plug-in and our user settings and it still says it is enabled.

Can you shed any light on this in regards to why it has stopped requesting the code but still says it is enabled.