I follow the link reply.

https://community.playfab.com/questions/40458/gamecenter-linking-fails-with-mysterious-error.html

but this code still not working.

How can i get signature code?

Social.localUser.Authenticate((bSuccess, msg) =>
                {
                    GameCenterSignature.Generate(OnSucceeded, OnFailed);
                });


[MonoPInvokeCallback(typeof(GameCenterSignature.OnSucceeded))]
    private static void OnSucceeded(string PublicKeyUrl, ulong timestamp, string signature, string salt, string playerID, string alias, string bundleID)
    {
        Debug.Log("Succeeded authorization to gamecenter: \n" +
            "PublicKeyUrl=" + PublicKeyUrl + "\n" +
            "timestamp=" + timestamp + "\n" +
            "signature=" + signature + "\n" +
            "salt=" + salt + "\n" +
            "playerID=" + playerID + "\n" +
            "alias=" + alias + "\n" +
            "bundleID=" + bundleID);


        var gamecenterRequest = new LoginWithGameCenterRequest()
        {
            PublicKeyUrl = PublicKeyUrl,
            Salt = salt,
            Signature = signature,
            Timestamp = timestamp.ToString(),
	    TitleId = PlayFabSettings.TitleId,
            PlayerId = playerID;
        };


	PlayFabClientAPI.LoginWithGameCenter(gamecenterRequest, result =>
                {
                    response.IsSucceeded = true;
                },
                error =>
                {
                });
     }