getting this error right after provisioning a new server
I got this as well but waiting a few moments and reload solved it.
Also i got this when deploying a site that wasn’t correct set up with a working entry point.
Try restarting Monitoring and NGINX on the server’s services tab. If that doesn’t work, then try uninstalling and reinstalling Monitoring.
It’s a known intermittent bug that’s been tricky to fix… 
actually just as @peterc said it works after few moments, I don’t know but my guess is because data is not yet available …
Awesome!
We did put in a new fix about a week ago - I guess it’s working. Just not right away… 