BLZWEBBMP20000008

This error is caused when you have the maximum number of game accounts associated with your Battle.net account. Each Battle.net account is allowed:

• Eight World of Warcraft game accounts.
• One StarCraft II game account.
• One Diablo III game account.
• One Heroes of the Storm game account.
• One Hearthstone game account.
• One Overwatch game account.

Note: If you are trying to purchase a game as a gift, you will need to click the Gift button in the shop.