Redeeming GV adds to total, not subtracts

I'm not sure what happened but I was doing a test checkout on my cart and went to go redeem a gift certificate and money was actually added to the total, not subtracted. Another weird thing is that its not adding just the amount of the gift certificate, but more. Add the less of your gift cert you use, the more it seems to add: (IE redeeming all of a $25 gv might add $50 to the total, but only using $10 of it might add $90).

So far I have added the ZenApple templete along with a columar mod for my product listings. I also rearrange the code for the product details page but haven't touched anything for gift certificates and I don't even know where to look to try to correct this. Can anyone help me figure out which piece of code might be messed up so I can try to correct this problem?

Also if anyone would like to try to actually see what I'm talking about my site is at https://www.fancypawsboutique.com/store if you send me your e-mail address I can send you a GV for you to redeem and try to test it for yourself. No worries, there's not payment processors set up yet, just click check or money order if the payment options if you want to try it out. Someone please help me.

Does anyone know what might be causing this problem? I can't open my store until this problem is resolved.

See these and determine if you have them setup correctly

https://www.zen-cart.com/tutorials/index.php?article=64

https://www.zen-cart.com/tutorials/index.php?article=336

I think the GV is installed and added correctly and the GV amount shows up in my test account like the amount is there. It even looks like the GV amount should be subtracted at check out but it's not. I took a piece of the checkout to show you. You can see it here:
http://fancypawsboutique.com/order.htm

Has anyone else ever had this problem?

I have narrowed it down to this problem only occurs when tax is also being added to the order. Anyone have any ideas on what I might have set up wrong?

I am having this very same problem. I just used it for the first time last night and the following happened...

Sub-Total: $119.98
Store Pickup (Walk In): $0.00
GST: $6.00
Gift Certificates: -$15.00
Total: $215.96

After looking through a bunch of other posts, I got this to work by setting Re-calculate tax as Credit Note.