https://underjollyroger.github.io/EarlyIllinoisLandcover
There is a 403 (Forbidden) error and the Mapbox tiles will not display when viewing from Google Chrome (zoom in six times with the mouse wheel to view tiles). I'm using a Mapbox API access token and the app is hosted from Github. The app works fine from Firefox.
Best Answer
This won't be the solution, it will just point to the most probable cause of the 403 error.
Here are request headers from three different browsers, where Firefox and venerable IE11 worked OK and Chrome failed.
IE11 (works OK):
Firefox (works OK):
Chrome (fails with 403):
What immediately stands out in Chrome headers are additional
Sec-Fetch-*
settings which obviously impose some additional restrictions regarding CORS policy, and it seems like Mapbox server does not like that.