Help with Deleted Theme

I understand how to download a theme from the site when i purchase. However, The problem is I downloaded it to wordpress and it did not work correctly and i deleted it. Now it will not let me download to wordpress again when i put in my purchase code. It says it can only be installed once. Please help. I can not afford $59 again

You need to deregister the theme

The process is different per theme so your best option is to ask the author