TorgosPizza,

Your first comment about the certificate not being "used up" is a concern. It definitely works with my version of the cart. Please test again and if you are sure this is happening, then I will test here with your version of the cart.

Regarding you later comment, the module should not be affecting anything to do with shippability. If you have a product that is non-shippable, then adding the attributes to "make it a certificate" could not affect this.

Cheers,
Darron