In-app Purchases not working correctly.

I have uploaded one of my app to give some paid service. But when the user tries to make an in-app purchase, it opens one screen like the title is "Apple ID, Almost there Payment request will be created for xyzdemo@ybl" After I press the continue button this window(Screen) closes automatically. But UPI requests are sent on the particular app. So why is this happening on my app? Why does this window (Screen) dismiss automatically?

I have also attached the screen.

This screen automatically dismissed.