Why does my Firestore collectionGroup query return an empty array when fetching subcollections?

I'm trying to fetch all subcollections named jobs from different customer collections using Firestore's collectionGroup query, but the returned list is empty.

I expect the query to retrieve documents from any 'jobs' subcollection across all parent collections. Below is the code I'm using:

SWIFTCopied
class JobListViewModel : ObservableObject {
    @Published var jobs : [Job]? = nil     
 
    func loadJobs() async throws {
        Firestore.firestore().collectionGroup("jobs").getDocuments {
            snapshot, error in
            if let error = error {
                print(error)
            } else {
                for document in snapshot!.documents {
                    self.jobs?.append(
                        Job(
                            id: "\(document["id"])" ,
                            position: "\(document["position"])" ,
                            salary: "\(document["salary"])" ,
                            state: "\(document["state"])" ,
                            city: "\(document["city"])" ,
                            description: "\(document["description"])"
                        )
                    )
                }
            }
        }
    }
}
        VStack {
            List {
                ForEach(viewmodel.jobs ?? [Job(id: "", position: "", salary: "", state: "", city: "", description: "")]) { job in
                    Text(job.city)
                    Text(job.position)
                }
            }
        }
        .onAppear {
            Task {
                try await viewmodel.loadJobs()
            }
        }

I have observed from a response that one common issue might be that the jobs array is not initialized, which could cause appending operations to fail. Can anyone advise if there are other possible reasons for the empty result, such as Firestore rules or naming inconsistencies within the database?