I have an idea - make it possible to buy gift codes

I'm trying to buy Minecraft Java Edition for PC for my nephew - unsuccessfully. The alleged 'system' for doing so is utterly asinine and unusable. As far as I can determine from the most recent Mojang post, gift codes can only be purchased on Amazon. I tried to do so, through the Minecraft store on Amazon. The system allows one to place the item in the basket. Except when one tries to check out, it returns a page stating 'Some items are no longer available. We're sorry. Some items became unavailable after you added them to your cart. In some cases, you can return to the product information page to try another seller.' HOW is it possible for a gift code to be unavailable? Can someone PLEASE explain how to gift Minecraft to another person.