On iOS and Android I do not have this problem. The only change I made is that for WinRT I used product IDS from the Add-ons section of the Window Store. The QtStoreSimulation.xml is deactivated.
My expectation was that this was all I had to do to use in-app products on WinRT platforms.
When I try to purchase something I get:
I also see this in my debug output:
My app is live here: https://www.microsoft.com/en-us/store/p/connect-water-pipes/9nhh0zcdzbm2
Is there something I am doing wrong? Does anyone else have this problem.