Unable to use my Apple balance

Do you have a valid payment method added to your Apple Account? It wouldn’t be used, but the system may be requiring a payment method other than gift cards. I do know that certain items are restricted. I have seen situations where a specific product in a specific color was not just not available.

>>Products at Apple Online Store, Apple Store App, or By Calling 1-800-MY-APPLE. When you purchase from the Apple online store, Apple Store app, or through 1-800-MY-APPLE, the funds will be deducted first from the amount available on any gift cards or codes you enter at checkout, and second from the amount available in your Associated Balance (if you are logged in to your Account and choose to apply your Associated Balance). Any unused amount will remain on your gift cards or codes or Associated Balance, respectively. If a purchase exceeds the amount available in your gift cards or codes and Associated Balance, another payment method on file or credit card you enter may be charged. If that is not available, you will be asked to pay with another payment method or the transaction will be cancelled. Gift Cards cannot be used for purchases in combination with Apple Pay or PayPal, or with payments split across multiple credit cards.

If you use a payment method on file to add funds to your Associated Balance, prior to charging the payment method on file, an authorization will occur for the amount of your purchase.<<

Legal - iTunes Gift Cards and Codes - Apple

I have also seen situations where the product could only be purchased by calling 1-800-MY-APPLE and speaking with an Apple representative. The product also had to be shipped and could not be picked up in store. Have you tried calling and ordering the device?

Do you have another payment method such as a credit or debit card entered? I know with the App Store that it will want to see something like those even if balance is ultimately used to make the payment. That, "Your payment authorization failed," make me think that. If I were in your situation -and pending hearing from Apple- I would try a debit card with a low balance in the account (say $100). Enough to let it see there is a card that works, but not enough so that if there is something odd at Apple's end it doesn't charge the whole $1900 to the card and still leave you with all that balance.

I know that with my bank I can have multiple sub-accounts. We have one split off from my main account that we use for travel. It has its own debit card and we keep a low balance in it. Enough to cover the costs of a small trip, but isolated from our main account so that should somebody steal the card they can't clean out our entire bank account.

Have a look at your payment methods and make sure any you have entered at still good (no messages in red). Add a payment method to your Apple Account - Apple Support From what you have quoted it sounds like something is not connecting, but I am just going by what it says. Otherwise this could be something happening on Apple's side just producing that message, in which case only they can really unravel what it is.

Remember that nobody on this forum works for Apple. I don't see that there is anything we can suggest that might help with this other than keep on trying with Apple and see if it an be moved to a more senior level. I have noted that comments similar to yours often involve rather large sums of money. I personally would not accumulate large sums like that in account balance.

What country are you in?