As Chris said, it's something that Itch just does sometimes for no reason that I - or anyone else - can discern :P
The APK is there, inside the ZIP file. Your device should come with an app for extracting the APK file, but if not you can download free ones from the Play Store, such as Files by Google ( https://support.google.com/files/answer/9048509?hl=en )
Hope that helps, and sorry for the inconvenience!