[Hummingbird] Hummingbird cannot test

I am trying to run a Hummingbird performance test but it is not working. It has worked without any issues previously but now I am getting the following error "The performance test didn't return any results. This probably means you're on a local website (which we can't scan) or something went wrong trying to access WPMU DEV."

The site is not local and it has never been local. The only thing that changed since the last successful test is that we installed and activated Defender Pro.