Hello Paul, thank you for this awesome plugin. I have it working on a normal set up out of the box but I'm trying to get it to work with the plugin URL Coupons (http://www.woothemes.com/products/url-coupons/) and it's just not working. Not sure if it's on your end or theirs.
My cart is currently set up to show the error.
If you go to http://bareminimumspanish.com/checkout/?add-to-cart=3558, the product is added to the cart. Enter 'tester' as the discount code and you'll see the custom message (awesome!).
But if you start over. And go the URL coupon way, http://bareminimumspanish.com/tester -- it only shows the original message.
Any help you can provide would be awesome.