The issue seems to be that the purchase or download button is not showing up. But you can still select the plane but since it was never downloaded you cannot load the airplane, therefore the default Cessna 172 is loaded instead.
For everyone experiencing this issue, were you all part of the beta program before or is there someone who never used the beta and can still not purchase or download the 737-800?
From which country are you connecting from? Perhaps some files are corrupted in our content delivery network which affects some countries but not others?
not beta before, no payment button, from Hong Kong