If you can see the episodes in your iTunes but the "Get" or "Get All" button is missing, there is way to resolve this. The solution is called: "Repair":
- Click on the Windows Start button on your bottom left screen and select "Control Panel".
- Now click on "Programs and features".
- Wait until the list is populated
- Look for iTunes.
- RIGHT click on it and select "Repair"
- Check iTunes
This should bring the buttons back. If that doesn't help then there is unfortunately only one other thing to do, and that is to uninstall and re-install iTunes.