Program installed & registered for me with no issues. It does exit once you enter the registration key, would be more comforting if it displayed a simple pop-up saying “We need to exit to complete the registration process”. But there were no Windows error messages. Win 10/64 Home.
I like the introductory video. This is a very different kind of paint program, and the video shows a simple example of how to use it. I’ve played around with prior versions, never quite grasping the power of this thing. My only suggestion: a link to the video should appear in the Help menu.