For the record—
I’ve tried seven or eight different packages using files from Ren’Py Launcher’s Web builder attachment. Ren’Py’s Documentation says the automatically generated zip file for the Web build has everything needed, but it really didn’t.
Some builds were missing files. The default code was wrong. Other lines I changed to ensure they match itch.io’s requirements that were vague about XHTML standards it allows.
After uploading the new builds, I get Error 403 when trying to run the embed on my itch.io project page. itch.io uses that “forbidden” error for a variety of problems.
The presplash or splash screen loads now that I corrected the file format in the code. Ren’Py Documentation from its Launcher says there isn’t a difference between .jpg and .png, which turns out to be untrue. The format must explicitly match for the splash image to load.
Nothing else from my game zip is loading. That’s when I get the “Error 403” message.
Could be that the Restricted state of the project page is messing with CORS (media connections) or some other web filter?