In flutter I wants to navigate when tapped on Material Button but its not working for below code is there anything wrong with response I am getting?

Question

I am getting this type of response when hit the API:{"token":"eyJhbGciOiJIUzUxMiJ9.eyJzdWIiOiJ2YWlzaG5hdmkuYXRkb2NodWJAZ21haWwuY29tIiwiaXNzIjoidGVjaC10cmFpbCIsImlhdCI6MTY3MjEyMjc2NiwiZXhwIjoxMjYwODgxMjI3NjZ9.a7Lq9v0fzMfwk5xCXuIfY4sh9Dls2Q0WksXtloui3OsoDwZBQX1qR6yJMz8nUS634POFETNxisHXTu6ObosEow"} Below is my code where I am checking if the response is not null then navigate to another page but its not working is there anything wrong with response type I am getting?

Center(
                            child: MaterialButton(
                                height:
                                    MediaQuery.of(context).size.height * 0.06,
                                child: AutoSizeText("Login",
                                    textAlign: TextAlign.center,
                                    style: style.copyWith(
                                      color: Colors.white,
                                      fontWeight: FontWeight.bold,
                                      fontSize: multiplier * unitHeightValue,
                                    )),
                                minWidth:
                                    MediaQuery.of(context).size.width * 0.5,
                                elevation: 3.0,
                                shape: RoundedRectangleBorder(
                                    borderRadius: BorderRadius.all(
                                        Radius.circular(30.0))),
                                color: Color.fromARGB(255, 253, 153, 33),
                                onPressed: () async {
                                  // _formKey.currentState?.validate();
                                  // final isValidForm =
                                  //     _formKey.currentState!.validate();
                                  // if (isValidForm) {
                                  final String email = emailController.text;

                                  final String pass = pwController.text;
                                  String pid = this.playerid;
                                  print(
                                      'The player id from login............${pid}');
                                  List<UserLogin> res =
                                      await LoginController.login(
                                          email, pass, pid);
                                  SharedPreferences prefs =
                                      await SharedPreferences.getInstance();
                                  prefs.setString(
                                      'email', emailController.text);
                                  prefs.setString('authToken', res[0].token);
                                  // UserLogin resp = UserLogin.fromJson(
                                  //     jsonDecode(res[0].token));
                                  print(
                                      'Auth Token.............${res[0].token}');
                                  // prefs.setString('username', res[0].userName);
                                  // this.uname = res[0].userName;
                                  // final String username = this.uname;

                                  String authToken = jsonEncode(res[0]);

                                  // ignore: unnecessary_null_comparison
                                  if (authToken != null) {
                                    Navigator.of(context)
                                        .push(MaterialPageRoute(
                                            builder: (_) => homePageAdmin(
                                                  this.playerid,
                                                  'Vaishnavi',
                                                )));
                                  }

                                  print(
                                      'Auth Token from login..... ${authToken}');

                                  // role == res[0].role;
                                  // print(res[0].role);

                                  // }
                                }),
                          )