Okay, I'll give it another go. When I tried to run, I got this line in the Debugger:
"Plugin "PlatformerPlus" was created for an older version of GB Studio and may not work correctly. Plugin uses engine "3.2.0-e4" but GB Studio is using engine "4.0.2-e0" and it never seemed to finishing compiling. I'll give it more time to see if it eventually completes.