I'm launching it directly from the Itch Launcher, where it opens its own window. Trying to launch index.html in Edge/Firefox/Chrome/Opera GX/Thorium/etc. all gives the same error:
Error
The following features required to run Godot projects on the Web are missing:
Cross Origin Isolation - Check web server configuration (send correct headers)
SharedArrayBuffer - Check web server configuration (send correct headers)
Thanks for reporting it. Seems like this is an issue specific to the itch.io launcher(?). Also idk about directly launching index.html. As far as I know, it is supposed to run on a local server (running index.html by itself does not open a local server). Can you try running the game from itch.io itself? The browser-playable version? It should work in that case. Thanks for your patience.