Apple does not anywhere say that you cannot use balance to pay for subscription arrears. What they say is that some on-going subscriptions may require the presence of a card but balance might be used to pay for them, or some current subscriptions may require payment using a card.
This article broadly outlines what you can buy with your Apple Account [Apple ID] balance --> What you can buy with your Apple Gift Card or Apple Account balance - Apple Support
• Pay for subscriptions like Apple Music, Apple Arcade, and Apple TV. Or pay for subscriptions to apps from the App Store.
• Pay for iCloud+, Apple's premium cloud subscription.
If you are seeing a request to enter a payment method, “Some purchases might require that you have a credit card on file, even if you use your Apple Account balance to make the purchase." In that case read this article about payment methods that you can use with your Apple Account --> Payment methods that you can use with your Apple Account - Apple Support then see this article about how to add a payment method to your Apple Account --> Add a payment method to your Apple Account - Apple Support
There are some exceptions, from: How apps, content, and subscriptions from Apple are billed - Apple Support
Apple Gift Card and Apple Account balance can't be used for some purchases:
• For some recurring charges, like AppleCare+, you can't start a subscription with Apple Account balance. But as long as you keep another valid payment method on file and your Apple Account balance would cover an entire charge, a recurring charge will pull from your Apple Account balance. In some countries and regions, Apple Account balance can’t be used for some subscriptions like AppleCare+.
• Some subscriptions might not be charged to your Apple Account balance.
So my interpretation of the problem you are having is that if you wish to still keep subscribing you may have to enter an approved payment method for Hong King, but make sure it is a card of some kind. Refer to this support article: Payment methods that you can use with your Apple Account - Apple Support
The alternative would be to cancel your subscriptions. I suspect if you have any money owing to Apple that they would be perfectly willing to accept any payment type for a debt, it may only be that to continue to subscribe you need something other than simply account balance.