can NOT fetch products

1. I created two auto renewable subscriptions in App Store Connect, and both their status is Ready to Submit;
2. I also created a sandbox tester in App Store Connect, and I logged it in on my phone settings>sandbox testers, I can it right there;
3. When I run my code on a real device, there's no product shows up.

Below is the source code of how I request products(I'm sure the product IDs are correct cause I have double-checked it), and it prints as the fetched result is nothing.

func loadProducts() async{
        Task {
            do {
                products = try await Product.products(for: ["MY_SUBSCRIPTION_ID_1", "MY_SUBSCRIPTION_ID_2"])
                // result is: products: []
                print("products: \(products)")
            } catch {
                // Handle any errors here, and no error raises
                print("Failed to load product: \(error)")
            }
        }
    }

This is the 1st time I'm trying in-app purchase, hope somebody can help me out, many thanks in advance :)