Hummingbird uptime monitoring error

When I try to enable uptime monitoring it gives me this error:

“Your domain does not appear to be publicly accessible on the Internet.”

What I found debugging on my own:

– The site is ‘publicly available on the internet’ (or at least you can type it in a browser and it shows up)

– Under WordPress General Settings, the site IS allowing access to search engines (not hiding)

– Is Hummingbird having trouble because it is a multisite installation?