Remove the homepage key from the package.json.
This is required when hosting on GitHub Pages as explained here or when building for relative paths. As stated in the Advanced configuration for PUBLIC_URL
Create React App assumes your application is hosted at the serving web server’s root or a subpath as specified in
package.json(homepage). Normally, Create React App ignores the hostname. You may use this variable to force assets to be referenced verbatim to the url you provide (hostname included). This may be particularly useful when using a CDN to host your application.