I'm using Win 10, Firefox 47. Neither my OS nor browser should be the issue, though, as I was using the same for the last two weeks with no problem on Glitch. It was only a couple of days ago the problem started occurring.
BTW I logged in and out, and the only difference that made is now the github import/export buttons are disabled, with 'Grant access to import and export to a repo' printed above the buttons. I try to click grant access, and I get the 'connection error - Our editor can't connect to the Glitch API. Is your computer online' dialog again.
Strange...I completed about 10 projects for freecodecamp using Glitch in the last 2 weeks, and it was only during the last project that I started having these problems. At least I was able to complete the last project, although I couldnt name it something meaningful or check it into github. Luckily I am done with my FCC Backend projects, so I won't need to use Glitch for now.