HTTP Requests on Angular not working

Lately, I added the capacitor framework to my Angular project to convert it to an Android app. But now I’m having issues with http requests to my Quarkus (a Java) server. I’m not getting an answer, and neither does the server. I’m not sure what the issue is because I don’t even get an error message in the Android Studio console; it just does nothing.
And is it possible to use the local storage feature on Android? Or do I need to use another framework feature?

And is it possible to modify the notification window? I want to build an music-app, and it would be nice to controll the services with buttons on a notification

export class HttpService {


  constructor(private http: HttpClient) {
  }

  login(username: string, password: string): Observable<any> {
    return this.http.post<any>(API_URL + "/auth", {username, password}, httpOptionsPost)
  }

  register(username: string, firstname: string, lastname: string, password: string, mail: string): Observable<any> {
    return this.http.post<any>(API_URL + "/user", {username, firstname, lastname, password, mail}, httpOptionsPost);
  }


  getAllUser(token: TokenModel): Observable<UserModel[]> {
    return this.http.get<UserModel[]>(API_URL + "/user/all", {
      headers: new HttpHeaders({
        'Content-Type': 'application/json',
        'Authorization': `Bearer ${token.token}`
      })
    })
  }

  getAllPlaylists(token: TokenModel): Observable<PlaylistModel[]> {
    return this.http.get<PlaylistModel[]>(API_URL + "/playlist/all", {
      headers: new HttpHeaders({
        'Content-Type': 'application/json',
        'Authorization': `Bearer ${token.token}`
      })
    })
  }
  getAllSongs(token: TokenModel): Observable<SongModel[]>{
    return this.http.get<SongModel[]>(API_URL + "/song/all",{
      headers: new HttpHeaders({
        'Content-Type': 'application/json',
        'Authorization': `Bearer ${token.token}`
      })
    })
  }
}
export const environment = {
  API_URL:'http://theUrlToMyServer:8080/api',
  production: true
};