Hello, I ran into this problem and I don't know what to do. I got upgrade coupons lvl 20 from a Quest i think and i got my lvl 20 equipment from shenron. The problem is that I can't upgrade anything with those coupons. I put my items in it and the coupon, then i click upgrade and it says SYSTEM FAIL or something like that. Anyonke knows how to fix it?
P.S I can upgrade with normal stones.
Upgrade coupons have bee disabled. discard them
you can upgrade with stones as long as they have same level or higher then the item you wish to upgrade with