[erikj]

It loads a blank page for me when I start a new canvas.

[rzzzt]

Your ad blocker might need to be disabled. I also had the same problem, but it worked after adding an exception for the page in uBlockO (the extension icon did not indicate that anything was blocked, though).

[max-m]

Had that problem on my first try in Firefox 57. It worked after reloading the page once.