Hey fox, if you're in the editing mode of Your stage, that is, the mode where you can press F5 to switch between Builder mode and play test mode, the end of Level doesn't work.
This is because if you were building a really big or eppic stage, like Remnant, for example, , and you accidentally stepped on the end of level square, EG, when testing out a boss at the end of the Level, you would get the congratulations! Level complete message, and you would be sent back to the in between levels area. Now you'd have to start building your stage all over again.
Yeah, frustrating, right?
That's why it doesn't work when you're in editing mode.
If you're in playing mode, however, I don't know what is wrong.