Hummingbird performance test didn't return any results


I've just installed the Hummingbird plug in on my Wordpress site and i'm getting the following notice :
"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"

I've tried to run it again a few times with no success.

Please let me know how to fix it