Why are in-app purchases being denied?

I'm seeking an alternative course of action, but wanted to check to see if others have had this same issue. I bought some Apple gift cards and added them to my account with the specific purpose of using them in an app while they're running a half off sale. I went to make the in-app purchase today and received a strange error message (Your purchase could not be completed...contact iTunes support...). So I contacted them this morning around 7 and they couldn't fix the issue and escalated the issue. Someone called me ~2 hours later, and they couldn't fix it either so they said 'give us up to 24 hours to fix this'. Well that doesn't work because the sale will be over by then. So I just called them back and asked for the balance of my Apple ID account to be sent to my cc (I figured out to how purchase via the same app on Android). Apple refused. So essentially they got me to buy their gift cards, but then won't let me spend the money. So I'm held hostage to their timeline to fix the issue.

For more context:

1) I waited a business day (8 hours) before I reached back out to complain which I think is very reasonable, especially considering that I've already missed one of the half off sales.

2) I've made in-app purchases through this app with no issues previously. Other users are purchasing fine. So it's not a problem with the app itself.