Use Atom to include the files in Premier, and it needs a purchase code, but in the license you give us in Elements, I don’t see any purchase code, just the license ID, I already try to add that, but doesn’t work.
I’d contact the author. While support isn’t included with Elements, the product doesn’t work without a purchase code, so they should help in this instance.
I left a question in their comments, here’s the reply…
Hi! Unfortunately, for Envato Elements customers, the use of the extension is not available. Use backgrounds manually. There is a tutorial for Envato Elements buyers in the “Help” folder To use the extension and receive a purchase code, you need to buy this product on Videohive