I want to play it again but I just cant
This article describes how you can get your steam key:
https://jni.itch.io/ancient-warfare-3/devlog/18776/steam-release-update-15
This is the itch.io article about how purchases work:
This article should help you:
https://itch.io/t/67604/how-to-get-a-steam-key-from-your-itchio-purchase
Otherwise, please contact the itch.io support.