OpenCart Community

When I try to use coupon code to order gift voucher, I get the following error continuously:

Error: Gift Voucher is either invalid or the balance has been used up!

But when I use the same coupon code to order any other product, everything works fine.

I can not find the cause of the error.

This isn't a bug, it's a normal restriction in eCommerce systems. Gift Vouchers are like cash. If they could use coupons to buy them at a discount, they could repeat the process indefinitely (buying more gift vouchers using the gift voucher they bought + another coupon) and rob you blind.