Unable to pay for Apple Music with account balance

Is Apple Account Balance supported as a payment method in your region?

Payment methods that you can use with your Apple Account - Apple Support

If yes, did you make sure that the Apple Account payment method is on top of the list of your payment details in Settings-> Your Name -> Payment &Shipping? You can reorder all payment methods if you tap on the Edit button.

Or are you getting an error message that this payment method can't be used?

Do you have an unpaid order or subscription?

If your payment method is declined in the App Store or iTunes Store - Apple Support

If all payment information is correct on your side, you should contact Apple Support about that, only they can look into your personal settings to find the issue.

Apple ID Payment Support

Or give them a call:

Apple Support Phone numbers