@kmingyeom That doesn't sound good. As per our new user policy, you won’t be able to complete transactions or redeem Gift Cards that are purchased outside the country or region of your residence. It's against the Play Gift Card Terms of Service. More info here: goo.gle/3zzRBsY.
@simyulsseu That doesn't sound good. Have a look at this guide to fix problems with Google Play gift cards: goo.gle/2Qd0Jhl. Hope this info helps.