Only the free version is available for download through the Itch app. The paid version can only be downloaded via the website.
Originally, the paid version was uploaded as an external file, and now I’m unable to convert it into a “native” Itch build. I can upload a new version as a separate build, but I’m not sure if people who already purchased the game will have access to this new build or if it will only be available to new buyers going forward.