Hello sumujsr04,
Let's see if the info in this guide helps you out:
"Some purchases aren’t charged to your Apple ID balance
- If you're in a Family Sharing group, purchases that you make are charged to your personal Apple ID balance. If you don't have enough Apple ID balance to pay for the purchase, the remainder is charged to the family organizer.
- You can’t use your Apple ID balance to buy gifts or gift cards.
- Some subscriptions might not be charged to your Apple ID balance."
We've found this in How apps, content, and subscriptions from Apple are billed. It might be that the subscription isn't allowing the Apple ID as payment. We'd suggest confirming this with them and if possible, make sure to add a different payment method until this is figured out. This way you won't lose access.
We hope this helped out!
Take care.