can’t associate icons with categories

I’ve gone through the support forums and haven’t been able to find an answer to this, so if I’ve missed it, please do point me in the right direction…

I’ve installed the “Category Icons” plugin, and as far as I can tell, I’ve done it correctly. It’s activated and I’ve set the local path and URL to my icons directory and uploaded a test icon. However, when I go to Category Icons > Manage > and try to select an icon, I get “no icon” as my only choice in the dropdown menu.

I suspect I’m overlooking something painfully obvious here, but I haven’t got a clue what it is. Any help would be greatly appreciated!

-Catie