Your e-mail does show up in my records. Try going going to "My Library" which is located on the top right corner next to your username and then from there, click on "Things you own" and see if you can find it in there. If you still can't find it, let me know.
I'm not sure why it won't let you.
Try following the directions here: https://itch.io/docs/buying/already-bought
If you don't get sent a link to download the files, let me know and I'll send you a key.