Some JavaScript & cookies have to be enabled for it to appear at the top of the page. If still no banner at the top of the page telling you you own the game, then you can send-in a ticket to itch - they should be able to help you, sending you an old copy of your game. Hope this helps. ~KC
Viewing post in The Zombie Asspocalypse - Chapter Zero comments
Go to https://itch.io/support after signing-into your account & select the button to "Email support@itch.io". After that, supply them with the email address you used to purchase the game. They should be able to help you from there if it's a currently valid email address. Good luck. ~KC