Customers can't add products to shopping cart

I’ve been getting a few emails for customers who are having difficulties adding products to their shopping basket, and so placing orders – not good!

When the “add to cart” button is clicked, it gives the following message… “Action failed. Please refresh the page and retry” When the page is refreshed and the “add to cart” button is clicked, it then says that the item was successfully add to the cart. But when “view cart” is clicked it says the shopping cart is empty.

Can you please help me with this? It’s fairly important as customers can’t place orders and so I’m losing business!

Thanks,
Sami

https://wordpress.org/plugins/jigoshop/