I'm sorry but, we don't have any control over the install process that happens on the Marketplace, we can't even look at the files, since they are encrypted.
The first thing to try is, of course, restarting the sim. The sceneries downloaded from the MS Marketplace are supposed to work with a restart, but sometimes this doesn't work, so you need to restart the sim.
Another thing you can try, is to remove the CONTENT.XML file found in one of these folders:
%LOCALAPPDATA%\Packages\Microsoft.FlightSimulator_8wekyb3d8bbwe\LocalCache ( MS Store version )
%APPDATA%\Microsoft Flight Simulator\CONTENT.XML ( Steam version )
On the next restart, a new one will be recreated, sometimes this fixes problems with sceneries not appearing.
