RecyclerView does not work sometimes when trying to display Firebase data

I have two RecyclerViews inside a LinearLayout in which I'm trying to display Firebase Storage data on one and some Products data queried from Real-Time Database on the other. While I am able to retrieve the data successfully, I have trouble showing it on the RecyclerView(s).

There are 1 of 3 things that happen spontaneously when I try to display the data:

• Case 1: Data does not show on both RecyclerViews OR
• Case 2: Data is shown for the first RecyclerView(displays storage data) OR
• Case 3: Data shows for both (but can sometimes take a verrryy long time to load even though I have only one data each for both).

For the second RecyclerView, I have written the code to query in-app products data from Google Play Console using the billingclient library and I use the data queried from Real-Time DB to see if there is a match in the product IDs. If there is, I display the matching data on the RecyclerView.

While fetching the data is fine, at various times my code gets stuck on setAdapter() and I don't understand why and I don't know how to get it to work properly?

Here's a reference to my current code:

@Override
public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup parent,
                         Bundle savedInstanceState) {

    FirebaseStorage storage = FirebaseStorage.getInstance();
    FirebaseDatabase database = FirebaseDatabase.getInstance();
    storageRef = storage.getReference(); 
    dataRef = database.getReference().child("products");

    view = inflater.inflate(R.layout.course_fragment, parent, false);
    mainLayout = view.findViewById(R.id.mainLayout);
    filesRv = view.findViewById(R.id.file_recycler_view);
    productRv = view.findViewById(R.id.product_recycler_view);

    //list storage folder/files
    listFilesFolders();

    //check for premium data on real-time database and see if productID matches with productID on Google Play Console (display data on recycler view if it matches)
    checkForPremium();

    return view;
}

private void checkForPremium() {
    setBillingClient(getContext());
    connectToGooglePlay();
}

private void listFilesFolders() {
    fileStorageRef.listAll()
            .addOnSuccessListener(listResult -> {
                for (StorageReference folder : listResult.getPrefixes()) {
                    parentFolder = folder.getName();
                    contentList.add(fileStorageRef.child(parentFolder));
                }

                for (StorageReference file : listResult.getItems()) {
                    fileName = file.getName();
                    contentList.add(fileStorageRef.child(fileName));
                }

                setFilesRecyclerView();
            })


            .addOnFailureListener(e -> {
                // Some code here
            })

            .addOnCompleteListener(task -> {
                // Some code here
            });
}

private void setFilesRecyclerView() {
    if(pageTitle.equals(rootFolder) || contentList.isEmpty()) {
        displayFolders();
    }

    else {
        displayFiles();
    }
}

private void displayFolders() {
    int columnCount = 2;
    DisplayMetrics displayMetrics = view.getResources().getDisplayMetrics();
    int width = displayMetrics.widthPixels; //get screen width

    //if screen width is large, increase  grid columns
    if(width > 800 && width < 1500){
        columnCount = 3;}

    else if(width >= 1500 && width < 1800){
        columnCount = 4; }

    else if(width >= 1800){
        columnCount = 5;
    }

    GridLayoutManager gridLayoutManager = new GridLayoutManager(getActivity(), columnCount);
    SubFolderAdapter subFolderAdapter = new SubFolderAdapter(getActivity(), contentList);
    filesRv.setLayoutManager(gridLayoutManager);
    filesRv.setAdapter(subFolderAdapter);
}

private void displayFiles() {
    LinearLayoutManager llm1 = new LinearLayoutManager(getActivity());
    fileAdapter = new FileAdapter(getActivity(), contentList);
    filesRv.setLayoutManager(llm1);
    filesRv.setAdapter(fileAdapter);
}

private void displayPremiumData() {
    LinearLayoutManager llm2 = new LinearLayoutManager(getActivity());
    productsAdapter = new ProductsAdapter3(getActivity(), billingClient, prodDetailsList, path);
    productRv.setLayoutManager(llm2);
    productRv.setAdapter(productsAdapter);

}

public void setBillingClient(Context context) {
    System.out.println("Set billing client");
    billingClient = BillingClient.newBuilder(context) //creates instance of billing client
            .enablePendingPurchases() 
            .setListener(this) 
            .build();
}

public void connectToGooglePlay() {
    //Establish a connection to Google Play
    billingClient.startConnection(new BillingClientStateListener() {
        @Override
        public void onBillingSetupFinished(@NonNull BillingResult billingResult) {
            if (billingResult.getResponseCode() ==  BillingClient.BillingResponseCode.OK) {
                // The BillingClient is ready. You can query purchases here.
                System.out.println("Billing client ready");
                listPremium();
            } else System.out.println("Billing client NOT ready");
        }
        @Override
        public void onBillingServiceDisconnected() {
            // Try to restart the connection on the next request to
            // Google Play by calling the startConnection() method.
            System.out.println("Billing service disconnected");
        }
    });
}

private void listPremium() {
    premiumDBRef.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot snapshot) {
            cProductsList.clear();
            for (DataSnapshot snap: snapshot.getChildren()) {
                Products products = snap.getValue(Products.class);
                String sku;
                String name;
                String url;
                if (products != null) {
                    sku = products.getProductId();
                    name = products.getName();
                    url = products.getUrl();

                    if(sku != null) {
                        skuList.add(sku);
                    }

                } else {
                    System.out.println("Product does not exist!");
                }
            }

            for(String sku : skuList) {
                productList.add(
                        QueryProductDetailsParams.Product.newBuilder()
                                .setProductId(sku)
                                .setProductType(BillingClient.ProductType.INAPP)
                                .build()
                );

            }

            if (!productList.isEmpty()) {
                querySkuDetails(productList);
            } else {
                System.out.println("No products available");
            }
        }

        @Override
        public void onCancelled(@NonNull DatabaseError error) {

        }
    });
}

public void querySkuDetails(List<QueryProductDetailsParams.Product> productList) {
    QueryProductDetailsParams params = QueryProductDetailsParams.newBuilder()
            .setProductList(productList)
            .build();

    billingClient.queryProductDetailsAsync(
            params,
            (billingResult, productDetailsList) -> {
                // check billingResult
                // process returned productDetailsList
                if (billingResult.getResponseCode() != BillingClient.BillingResponseCode.OK) {
                    System.out.printf(Locale.ENGLISH, "Unable to query sku details: %d - %s%n", billingResult.getResponseCode(), billingResult.getDebugMessage());
                } else {
                    for (ProductDetails details: productDetailsList) {
                        prodDetailsList.add(details);
                    }

                    displayPremiumData();
                }
            });

}

Note: When I run the code, there are no errors. The issue is that the RecyclerView is not working consistently as intended. I have been trying to get this to work but I have been stuck for days now and I would really appreciate some help please!