Angular2: Why does 'else' not get executed in subscribe function?

I'm trying to verify that the response email field matches the email to the user who is logged-in. When I navigate to an URL (detail/:id) which was set up by another user and doesn't belong to the currently logged-in user, Angular should display an error message. So far so good. But in my case, the else function, to display the correct response does not get executed.

This is my code:

export class AppointmentDetailComponent implements OnInit {
  username = '';
  email = '';
  message;
  messageClass;
  getData: any;
  appointmentDetails = [0];
  id: number;
  private sub: any;

  constructor(
    private authService: AuthService,
    private apiService: ApiService,
    private route: ActivatedRoute
  ) {}

  ngOnInit() {
    this.sub = this.route.params.subscribe(params => {
      this.id = +params['id']; // (+) converts string 'id' to a number
    });
    this.getData = this.getDataFunction;
    this.getData();
  }

  getDataFunction() {
    this.authService.getProfile().subscribe(profile => {
      this.username = profile.user.username; // Set username
      this.email = profile.user.email; // Set e-mail
      if (profile.user.email) {
        console.log(this.id);
        this.apiService
          .getAppointmentDetailsById(this.id, this.email)
          .subscribe(appointmentDetails => {
            if (!appointmentDetails.success) {
              this.messageClass = 'alert alert-danger'; // Set error bootstrap class
              this.message = appointmentDetails.message; // Set error message
            } else {
              console.log(appointmentDetails);
              this.appointmentDetails = appointmentDetails;
            }
          });
      }
    });
  }

  ngOnDestroy() {
    this.sub.unsubscribe();
  }
}