The default room works for me as well (but I havent tried exporting the whole project into another one).
The default room is basically a pinball table stripped of everything, just flippers, plunger, ball, ... as a nice starting point.
Does the ball not launch, or does it go up but hits something invisible so that it can't exit?
At the end of the plunger lane is a single-pass-through invisible wall capsule. It is used so that when the ball does exit the plunger lane, it can no longer go back inside during gameplay. It's possible there might be something going on there, but I think I need a bit more details since it works on my end.
