Amazon made a change today and stopped allowing the use of an Amazon gift card or Amazon gift card balance to pay for the purchase of third party gift cards or e-gift cards (affiliate link here and below). Ouch.
It was never possible to pay for Amazon gift cards or Visa gift cards with your Amazon gift card balance. But it had been possible to pay for third-party gift cards with your Amazon balance, such as Starbucks, Apple, Chipotle, Best Buy, Albertsons, etc. Now the system is coded not to allow that.