In the documentation for ValidateWindowsStoreReceipt, the parameter section lists CurrencyCode and PurchasePrice is marked as required, but is not present in the request example. Also, the receipt in the request example does not seem to be an XML.
The error code section has a reference to "MissingAmazonSharedKey", which does not make sense to me.
I wonder if anyone from PlayFab could take a look at this and make sure that these are intended?
https://api.playfab.com/documentation/client/method/ValidateWindowsStoreReceipt