Back to Cart?

After a card attack I've set up the only accept calls from my domain, but just realised that this has stopped the back to cart button from working.
Last blocked URL : https://secure.romancart.com/

Any ideas or can roman cart be added in the background as a default?

If you try https://www.nfed.co.uk/shop/classifieds.htm & get to the checkout, then try the back to cart link
"Unable to add to the cart. Please contact the merchant and quote code 'AZ5263'
The cart is not configured to be accessed from this URL."

In the security section I have: Only accept calls to the cart from: nfed.co.uk
Last blocked URL : https://secure.romancart.com/

The link in the checkout page is
<div class="ROC_Left"><a href="//www.romancart.com/cart.asp?storeid=62023"><img src="https://secure.romancart.com/secure/images/5336KGK62023FGFJ1.png" alt="Return to Basket" width="120" height="31" border="0"></a></div>

It worked with http:// but triggered the unsecure warning. https:// or // is blocked.

Thanks

Just a quick update on this.
I've created a redirect page which the Return to Cart button now goes to.
The new page bounces straight to the cart, as it comes from my domain, all works OK.