RequestProductPurchaseAsync throws "Cannot change thread mode after it is set"

Windows UWP
1

Hi there,

I´m trying to implement a in-app-purchase-functionality and get an exception when I´m calling RequestProductPurchaseAsync. It states:

 Cannot change thread mode after it is set. (Exception from HRESULT: 0x80010106 (RPC_E_CHANGED_MODE))
 at Windows.ApplicationModel.Store.CurrentAppSimulator.RequestProductPurchaseAsync(String productId)
 at Crocs_World__Xbox_Edition_.App.<BuyFeature>d__7.MoveNext()

That´s what I´m doing:

  public async Task LoadInAppPurchaseProxyFileAsync()   
     {
         StorageFolder proxyDataFolder = await Package.Current.InstalledLocation.GetFolderAsync("data");
             StorageFile proxyFile = await proxyDataFolder.GetFileAsync("in-app-purchase.xml");
             licenseChangeHandler = new LicenseChangedEventHandler(InAppPurchaseRefreshScenario);
             CurrentAppSimulator.LicenseInformation.LicenseChanged += licenseChangeHandler;
             await CurrentAppSimulator.ReloadSimulatorAsync(proxyFile);

        // setup application upsell message
        try
        {
            ListingInformation listing = await CurrentAppSimulator.LoadListingInformationAsync();
            var product1 = listing.ProductListings["product1"];
            var product2 = listing.ProductListings["product2"];               
        }
        catch (Exception e)
        {
            Debug.WriteLine("LoadListingInformationAsync API call failed:" + e);               
        }
    }

    private async void InAppPurchaseRefreshScenario()
    {           
        Debug.WriteLine("InAppPurchaseRefreshScenario");
    }

    public async Task BuyFeature()
    {
        LicenseInformation licenseInformation = CurrentAppSimulator.LicenseInformation;
        if (!licenseInformation.ProductLicenses["product2"].IsActive)
        {
            Debug.WriteLine("Buying Product 2...");
            try
            {
                await CurrentAppSimulator.RequestProductPurchaseAsync("product2");
                if (licenseInformation.ProductLicenses["product2"].IsActive)
                {
                    Debug.WriteLine("You bought Product 2.");
                }
                else
                {
                    Debug.WriteLine("Product 2 was not purchased.");
                }
            }
            catch (Exception e)
            {
                Debug.WriteLine("Unable to buy Product 2." + e);
            }
        }
        else
        {
            Debug.WriteLine("You already own Product 2.");
        }
    }

Whenever I call BuyFeature it throws the exception. Except if I call it right in LoadInAppPurchaseProxyFileAsync. Then it seems to be the same thread.
If I replace Task with void in both Methods it doesn´t work either.
Does anybody have an idea what I’m doing wrong?

Thank you,

Harry