problem with download.
I recommend attempting to use a different browser or using the Itch.io desktop app, which you can find here: https://itch.io/app
Unfortunately, this sounds like an issue directly related to Itch, meaning I don't have direct control over it. However, the solutions I offered above should work.
If you don't have another browser installed you could also try temporarily disabling your adblock: as it may be preventing the button from working.