I've just checked and double-checked and according to jwt.io I have a perfectly valid ES256 token, which resolves to the same shape expected by Apple in the documentation, shape: { "alg": "ES256", "kid": "ABC123DEFG" } { "iss": "DEF123GHIJ", "iat": 1437179036, "exp": 1493298100 }

I can even decode the token presented in the authentication window: https://authorize.music.apple.com/woa?a=[[TOKEN_THAT_VALIDATES_PERFECTLY]]&referrer=[[MY_WEBSITE_URL]]/&app=music&p=subscribe

The app itself is able to communicate with Apple Music API just fine, it works perfectly using the same token encoding function that I use and return to MusicKit JS. So it's definitely a problem on Apple's side.

@0132 - any chance you've solved this? I'm getting the EXACT same behavior now out of the blue after 4 years of my app working perfectly...