Hello, again; no problems, feel free to ask.
There's an open issue to make the tool display the error messages in a convenient way:
https://github.com/haroldo-ok/vcs-game-maker/issues/10
But, until it is implemented, the only way to see what error is happening is to look at the browser's console; try pressing F12, then clicking on the "Console" tab and checking what error messages appear there.:
https://screenful.com/guide/how-to/how-to-open-the-browser-developer-console