it's possible (I have not used itch on mobile before)
normally you should find it in the download section:
do you see a "You own this game" banner when you visit https://mutantleg.itch.io/zortch ? 🤔
Edit: I checked on chrome, it should look something like this:
I checked out the support docs: https://itch.io/docs/buying/already-bought
the keys have been refilled and I see that they are getting claimed by others (this part seems ok)
maybe it's this auto fraud detection thing having a malfunction? 🤔
anyway, please try to contact their support: support@itch.io