In app purchase testing in iOS

I am using Xcode 8.0, Swift 3.0 and testing in app purchases in my iPad. I want to test in app purchases using sandbox user.

There is no account added in device's Setting

The Problem is I am not getting product list in response of product request code. Please take a look on my code:

let PRODUCT_ID_MY_PRODUCT = "com.company.ProjectName.MyProduct"
// The ProducID in this code and ProducID on iTunes are the SAME. ✔️

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)

    if productID == nil {
        productID = PRODUCT_ID_MY_PRODUCT
    }
    SKPaymentQueue.default().add(self)
}


override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)

    startPurchases()
}

func startPurchases() {
    if (SKPaymentQueue.canMakePayments())
    {
        let productIDs = NSSet(object: self.productID!)

        let productsRequest:SKProductsRequest = SKProductsRequest(productIdentifiers: productIDs as! Set<String>)
        productsRequest.delegate = self
        productsRequest.start()
    }
}


// Delegate Methods for SKProductsRequest
func productsRequest (_ request: SKProductsRequest, didReceive response: SKProductsResponse) {
    let count : Int = response.products.count
       // THE PROBLEM IS HERE.. I AM GETTING COUNT IS ZERO.. MEANS response.products returning null ARRAY
    if (count>0) {
        let validProducts = response.products
        for aProduct in validProducts {
            print(aProduct.productIdentifier)
        }
    } else {
        DispatchQueue.main.async(execute: {
            UIAlertView(title: "Purchase !", message: "Product not available", delegate: nil, cancelButtonTitle: "OK").show()
            return
        })
    }
}

So..... That's the problem: I am getting response.products null (no data in array) so Please help me to find the solution. You can see the comments in code: // THE PROBLEM IS HERE.. I AM GETTING COUNT IS ZERO.. MEANS response.products returning null ARRAY

I created products over iTunes Connect. You can see the image below. All the products are in "Ready to Submit" state.

There is some warning on iTunes

Your first In-App Purchase must be submitted with a new app version. 
Select it from the app’s In-App Purchases section and click Submit.


Once your binary has been uploaded and your first In-App Purchase 
has been submitted for review, additional In-App Purchases can be 
submitted using the table below.

And

I also created Sendbox user for testing In-App Purchases. See the image below:

Did I miss something? Or what is the error? And where is error? I want to test in app purchases using sandbox user

I fixed this. There are some points need to careful about. See below:

Make sure your developer account did the paid application contract. see image below:
Create Products on the iTunes Connect.
Implement In-App-Purchases code and configuration settings.
Create one build with Distribution profile.
Upload build on store. Add build to current version. Add In-App-Purchases to the version on iTunes Connect.
Then try to test, if still not then submit app once then cancel it. then after try to test on your device.
Make sure when you test with sandbox user, you need to sign-out from your already logged in account from device settings, and login with sandbox ID.
some screenshots might be helpful.