Blurry Fish Eye Lens Photos?

I got a fisheye lens and it was mighty expensive. Its a Japan optics HD digital advance 0.48x52mm. I'm using it on my Nikon D3100 18-55mm lens and it never focusses. Ever. I've tried many things (auto/manual focus, 3D setting etc) but nothing seems to work. Are there any suggestions? It worked when the guy at the store demo'd it to me.

Bring it back that guy

Doesn't sound like a lens, but an adapter. A fish eye lens will be put on just like the 18-55mm, not on top of it.
Did it work on YOUR camera?
I'd return it and ask for a refund.
Most all push on adapters are junk…

Take it back to the shop and ask them to show you how it worked then but not now.
It's probably just an adaptor or filter, not a proper lens.

What you bought is a cheap screw-in attachment that supposedly makes the 18mm end of your 18-55mm zoom wider than 18mm. In all likelihood it only functions when you're using the 18mm end of your zoom. If it came with instructions read them. If not, take it and your camera to where you bought it and ask for help.

Not strictly a fish-eye lens, but an "adaptor". Very few of those sold are any more than bottle-glass, and I'm sorry that you paid a lot of money for it - most are cheap in price as well as performance. Very few work well with zoom lenses. Try to get your money back.

I bought the same thing but a 0.21x lens and it is the same. It doesn't focus properly. Better off saving and buying a proper lens like a Nikkor 10.5mm fisheye, although they're around $800.