Check Out page won't work

I did everything as instructed.
But when I click on buy now button it brings me to same page(where you make the buy now button clicked)
Where I am going wrong?
Yes I did create check out page with codes.

You can check error on http://www.lietissimo.com/unique-rings/ page first product.

Any help would appreciated so much.

Thank you.

https://wordpress.org/plugins/simple-cart-buy-now/