Unfortunately as of now, itch unlists from the website any game that accepts any form of payments. Because of that we've been forced to remove any payment options from itch to avoid being shadowbanned.
The game always had a free version hosted on itch, even when it was marked as paid, so we just decided to only leave the free version which will be one update behind the paid version.
Once we release on Steam, we'll put the paid version back up on itch so that everyone that has already bought the game, can't buy it off of Steam, or wants to play the android version, can still enjoy the game.