Fail on purchasing in via Windows store

I'm trying to purchase item via win store. It is always worked, until today.

In this place:

receiptString = await CurrentApp.GetProductReceiptAsync( product.ProductId );

I got this: "Internal server error" (500).

And this: An unknown error has occurred on our side. Wait for a while and then try again. Error code: 0x801901f4

But money is withdrawn from the card