Sometimes there are issues with exporting to OBJ at the moment. Try saving your work, closing the app and then reopening it. This usually fixed OBJ export.
If not then try keeping your scenes simple, using as few shapes as possible.
Thanks for playing. Yes there is no replay / restart button in this version. The simplest way to restart a level is to fail the level (get yourself killed). This will then allow you to replay that level. I hope you enjoyed the game apart for that :)
