Would really appreciate support with this invalid_client issue: I have a web app and have aligned the JWT Header and Payload JWT Header { "alg": "ES256", "kid": "ABC123DEFG" } JWT Payload { "iss": "DEF123GHIJ", "iat": 1234567890, "exp": 1234567890, "aud": "https://appleid.apple.com", "sub": "com.yourapp.service" The domains and callback are aligned and correct I've even created a new p8 and updated the Key_ID Sending Credentials to Apple (Token Request) Content-Type: application/x-www-form-urlencoded However, still no luck. Can anyone assist with identifying the possible error? Many thanks