This can have several causes and there are a few known issues with Ren’Py (the game’s engine) which are listed here in the documentation together with solutions.
If the game doesn’t start at all on Windows a possible solution is to update or reinstall your video drivers. Also, make sure the game is installed in a location in a directory with a full path that is representable in the current system language. So installing the game in a directory containing Chinese characters while the system language is set to English will probably lead to problems.
If the game doesn’t run on macOS it could be quarantined by GateKeeper you can try the following:
- Open Terminal.app
- Write the following command:
xattr
followed by a space and drag the TFTUV.app or SL.app from the Finder onto the terminal window
- Press Enter, it should show
com.apple.quarantine
as a result. If the text is not shown you’ve likely encountered another issue.
- If the text is shown, type
xattr -d com.apple.quarantine
followed by a space and drag TFTUV.app or SL.app onto the terminal window again
- Press Enter and try to launch the game again.