Hummingbird - The performance test didn't return any results.

Hi Guys,
When I run Hummingbird I get the following result. Any idea why?

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. Try again and if this error continues to appear please open a ticket with our support heroes

Cheers
Simon