Can't redeem gifts

When I try to redeem gifts (xbox game pass and youtube premium) it simply won't work and it won't state why. I think I might have goten the gifts from being a Nitro customer and I'm seriously considering unsubscribing simply because of this.

My guess is that it's those really stupid type of codes that only work if you aren't already a customer (since why would you appreciate a customer when you've already take their money?). It's a source of irritation to be given a code that you can't use simply because you are already a subscriber. It makes gives me a distaste for both the service and, unfortunately for Discord, the giver.

Please stop the practice of punishing paying customers, it's insulting.