Why are certain gift cards not in the add selection box for a purchase order?

The add gift card name selection box for purchase orders only contains gift cards for that vendor. Therefore if the gift card you need to add is not in the list, ensure that the gift card vendor is correct. You can change a gift card's vendor in the gift card settings (Administration->Gift Cards->View Gift Cards).

The reason the selection box only contains gift cards for the vendor of the purchaser order is to reduce data entry errors. It also reduces the gift card list to make finding the gift card you need to add easier.