If the original customer purchased an email GV he should have received an automated gift redemption certificate by email from you. He would have then clicked on the link contained within the email for this express purpose. This would have taken him to your site and redeemed the GV.

If another person was given the email this new person would have been asked to create an account, and the gift certificate would have been validated and placed in the new person's gift account ready for use.

I believe that the original customer never received the automated email gift redemption certificate from you.

Others will need to provide you additional information as to why that email was not generated. All I can tell you is what I understand is the standard process for email GV.

You may want to read https://www.zen-cart.com/tutorials/index.php?article=64

Sawhorse