Apple account balance for purchases

This is my first go round for getting an Apple GC for the SWGOH promo.  I redeemed it so I have a balance in my account but I am unable to use it for webstore or in game purchases.  I contacted Apple support and they said only certain apps/websites  support using the balance and apparently SWGOH isn't one of them??   One of the reasons I bought the card was to be able to use it for purchases with the game.  I have a balance sitting there I can't use.  I think it's crazy to run this promo and you can't use the money to make purchases for the game.  Has anyone else encountered issues?  Am I doing something wrong?