Hello, it's been about six days since my original comment. I was wondering if you where able to find the source of the problem and if so how to move forward from there?
No, I'm sorry. For the black screen it might simply be because the game is struggling to run. If you shut off the blinking animations and don't run other things in the background it may work better. But the pop up error isn't something that can be fixed quickly because it will require remaking/uploading the entire build.