Hmm I've run through the process along with some of the other developers, everything seems to work. What internet browser are you using? We found that using Chrome and being signed into a google account always worked.
Tried using Firefox, Chrome and Edge, logged in and not. Every time still the same fatal error. If there is any other info you need from my end, I'd be more than happy to provide it.
We are currently looking into getting more space to accommodate the game, so we don't have to use an external site. I will message you as soon as we know if we can get more.
I have no idea what could be wrong. I haven't received word from anyone else with these issues. If there is any way I could try sending you the game let me know.
I feel bad for seemingly being the only one with these issues. I'm @ReallyCoalFire on twitter or coalfiregames@gmail if you'd like to speak more directly to get this all figured out! I do appreciate and respect all the extra effort you've gone to already.