Angular 9: forkJoin subscribe not working

I’m trying to load page data on a top level component in Angular 9 using observables. When I subscribe to each of these services individually, I can see the data coming back just fine:

ngOnInit(): void {
  const technicianSubscription = this.techniciansClientService.getByTechnicianId(this.technicianId).subscribe(technician => console.log(technician));
  const technicianReviewsSubscription = this.technicianReviewsClientService.getByTechnicianId(this.technicianId).subscribe(technicianReviews => console.log(technicianReviews));
}

When I try to use forkJoin, the data from the subscribe method is never returned:

ngOnInit(): void {
  this.pageDataSubscription = forkJoin({
    technician: this.techniciansClientService.getByTechnicianId(this.technicianId),
    technicianReviews: this.technicianReviewsClientService.getByTechnicianId(this.technicianId),
  }).subscribe(
    // data is never logged here
    data => console.log(data)
  );
}

I’ve tried passing forkJoin an array of service calls and I’ve tried using zip as well, to no avail. What’s happening here?

Source: Angular Questions