Hi,
The "add to cart" at the bottom is a link that you added in the description of your product and that link is wrong.
You used the link:
http://www.workingtrials.info/shop/hikashop-menu-for-products-listing/product/updatecart/quantity-1/checkout-1/cid-1
As you can see, in that link, you have set the parameter "cid" with the value "1". Which means that when you click on that link, it will add the product with the id 1 to the cart.
But as you can see in the URL of the page (
www.workingtrials.info/shop/hikashop-men...-dog-to-want-to-stay
) , the id of the product is 4.
So it's actually trying to add another product than the one on that page. Maybe you don't even have anymore a product with the id 1 since when you try to open the page
www.workingtrials.info/shop/hikashop-men...-dog-to-want-to-stay
the website says that this product with the id 1 is not found.
Which explains why the cart system didn't allow you to add it to the cart.