The Mission Control Preview isn't working, and thus missions cannot be shared.

I've tried multiple browsers, devices, epic, dogfight, lots of text, no text, minimal text.

It simply does not work anymore, I've been retrying a few times a day for 3 days, and always get the same result: the popup saying it's preparing the preview, then the popup disappears and nothing happens. I can leave it for hours, it makes no difference.