Why isn't subscribe initialized when visiting the page again?

Question

Angular

Basically there is an app. 2 pages ..... when I'm on the main page and go to 2 .... everything is ok ... but when I go to the main page and back from the second page, the function from the service does not start again ... the page becomes empty ... and the function does not work in ngOnInit
// Services

export class CommonDataService {
  private question = new Subject<any>();

  changeQuestion(boolean): void {
    this.question.next(boolean);
  }

  getQuestion(): Observable<any> {
    return this.question.asObservable();
  }

}

export class ApiService {
  getQuestionsData(params?: string) {
    params = params || '';
    if (params) {
      params = '?' + params;
    }
    return this.getTemplate('/q' + params, {}).subscribe((data: any) => {
        this.commonData.changeQuestion(data);
    });
  }
}

// component

ngOnInit() {
   apiData: Subscription[] = [];
    const langSub = this.commonData.getQuestion().subscribe((data: any) => {
    });
    this.apiData.push(langSub);
  }

  ngOnDestroy() {
    this.apiData
      .forEach(s => s.unsubscribe());
    // }
  }