We're using v1.5.6b with a compatible version of PHP. We haven't run into issues with gift certificates in the past 10 years. After running into an issue where a gift certificate was released but not added to the database, I need to test the process of purchasing a gift certificate. I have created a coupon with these settings:

Coupon Name :: Testing Coupon
Coupon Amount :: 100.0000% Per Order
Start Date :: 12/23/2023
End Date :: 12/24/2024
Uses per Coupon :: Unlimited
Uses per Customer :: Unlimited
Valid Product List :: --none--
Valid Categories List :: --none--
Coupon Minimum Order :: $0.00
Coupon Minimum calculated from: :: All Products
Date Created :: 12/24/2023
Date Modified :: 12/24/2023

Coupon Zone Restriction: :: 0

Customer previous Orders less than: :: Unlimited

Coupon valid for sales: :: Coupon IS allowed for Products on Sale

Every time I try to check out with a gift certificate, it says it is not valid for any product currently in my cart. I specifically have no restrictions on the coupon and on the gift certificates themselves I see no where in the product info that it is not viable for a coupon. How can I make this work, or more importantly; how can I test purchase of a gift certificate so I can then follow it through the DB and make sure records are being created properly throughout the release process?