Why can I no longer download my seasonal pass to the computer?

Make sure you're using the same Apple ID that you used to purchase the season pass by clicking iTunes > Store > View Account. Also, check for Available Downloads in the same menu.

If you aren't sure how to complete your Season Pass downloads, see this Apple doc -> iTunes Store: Download options when purchasing TV seasons, Season Passes, Multi-Passes, movie bundles, music box sets, or individual movies or TV episodes