Which site did you purchase it from? Will look into it.
Viewing post in KR Ultimate Sci-Fi Frontiers RPG Tileset comments
I don't see a record of that purchase being completed so I wonder if something went wrong with the purchase itself. Were you charged for it? If you were, you probably need to get in contact with itch.io tech support and let them know about it. I wouldn't be able to do anything about that, I'm sorry to say.