Trovo's Developer Panel has an "Interactions Endpoint URLs" list which doesn't mention CORS, but appears to control which origins CORS works with. Make sure to add your origin to that list for it to work.

Special bonus tip: for local files, you need to add "null" and/or "http://absolute" (such as in OBS) instead of a URL. The interface doesn't directly let you add these values, but you can fake it with CURL..