In the app the red button just says "Open page" instead of the usual install button.  Clicking it opens the https://unboundcreations.itch.io/headliner-novinews page in my browser, where I can manually download the game.

Bit odd that the app can't do it though.

Oh, I can't manually download it directly from that page, my mistake.  I did download it from the bundle download page though - the "You own this game - DOWNLOAD" button at the top of the game page.

Never mind.  Fixed by the developer - see https://itch.io/post/1532414.