In theory, just wait for the player to finish the level, and then press ENTER.
Some players reported problems playing in Firefox, maybe it's a bug that only happens in the browser you're using, in general it works better in the most updated Chrome.
Tested in chrome version 114.
If it doesn't solve it, I would like to know if there are any error messages, or if there is a way to take a print of the part that stopped, that would be excellent too.
Sorry for the inconvenience :(