Sign in with Apple ID => Ionic Support?

Because “this” cannot be read inside function(). You should try using arrow function. Which is remove the “function” and add “=>” after (succ). Such as;

cordova.plugins.SignInWithApple.signin(
        { requestedScopes: [0, 1] },
        (succ) => {
          console.log('succ');
          console.log(succ);
          this.DService.AuthUser(succ).then((res :any) => { /* this is not working under this function */
            console.log('Result');
            console.log(res);
          });
      });

Hope it helps.