Hi, I followed step by step documentation to implement SignIn with Apple in iOS/Android application. I created an AppId com.nhp.queenergy, a related ServiceId com.nhp.queenergy.apple, and a KeyId. Authorization request is correctly performed by using ServiceId as client_id and my backend redirect_uri I receive code on my backend Token request is performed by using ServiceId as client_id, same redirect_uri, the code I have just received and the client_secret as JWT signed with my .p8 certificate with the following decoded structure Header { "kid": , "typ": "JWT", "alg": "ES256" } Payload { "iss": , "sub": "com.nhp.queenergy.apple", "aud": "https://appleid.apple.com", "exp": 1756113744, "iat": 1756111944 } I always receive "invalid_grant" error without any further error description. Moreover the error is always the same even though I use any fake string as client secret. If the code expires, as expected the error changes by adding "The code has expired or has been revoked." I really don't know how to solve this issue Best regards