Apple gift card issues

hello, I have 3 iPhones that my nieces have and they have three iphone gift cards that I just bought them, but they’re trying to use $100 credits on a game called Genshin impact, but it’s showing errors and issues. Images of the issues are sent below. They have the apple itune gift cards with money credit in them but the game is not allowing them to purchase within the game. If that makes sense. Could you please call to help so I can tell my nieces how to use there apple gift cards in the game?