I'm having the same issue. It keeps opening that up and then, if I press ignore, it opens the game but in quite possibly the smallest window I've ever seen. No maximize button either :(
Hi! Thanks for the heads-up about the bug. I just updated the Mac version to fix the small window and the "game not found" issue. Although I wasn't able to recreate the error message above. Please let me know if it shows up again, and thanks for playing!