If you paid 10usd for a previous chapter, in the My Library section of your account you can find the game and download the latest one. It should work as long as the price does not increase.
I've experienced the same and have paid the amount shown on Itchio. Where is this 'My Library' section? I see I'm not the only one having this problem so suggest the instructions for downloading need improving as I'm going to 'download now' and ending up with a bum steer!
