This error occurs when the in-game shop is currently closed.
Purchased Heroes of the Storm Gems for the Wrong Region
Tools required for opening a Blizzard Data file.
What to do if you buy a WoW Token for real money in the Blizzard Shop but you don't see it in your inventory
How to cancel, return, or exchange a Blink Shopping order during or after BlizzCon
Game Time can be purchased through the Battle.net Shop instead of a subscription
Battle.net Balance top-ups may take up to 24 hours to be available for use
What to do if you get the error “The Offer is Not Available?” when purchasing a product offered at a discount.