Having problems downloading Everyone's Gone to the Rapture from PlayStation Store? Sony have tweeted a solution.
Log in and click on the Everybody's Gone to the Rapture promo image on the Store's front page, or search for it. Then click the Wishlist heart. If you click to go through to the gamepage you will encounter the "this item isn't available right now" error.
But if you add it to your Wishlist, and then go to your Wishlist, you can Add to Basket direct from there. Then View Basket, Proceed to Checkout, Order & Pay (nothing), then Download to PS4 from your Download List.