The character is unavailable for use. Possible causes for this error are listed below.
Pending Character Service
Once you initiate a character service, your character is unavailable until the process is complete. The estimated processing time is provided when you start the service.
You can check the status of your character service by visiting the Transaction History page in Battle.net. On this page, choose the appropriate character service and click History/Status to view the status of the service.
Note: If your payment has failed or the transaction is stuck, click the Cancel link on the History/Status page to cancel the transaction and unlock your character.
Character Boost: Failed or Charged-Back Payment
If you purchase Warlords of Draenor® or a Level 90 Character Boost and your payment fails or is charged back by your financial institution, the character you boosted is locked until we receive repayment. To repay:
Warlords of Draenor
Level 90 Character Boost Service
Expansion Level Issue
If your World of Warcraft expansion purchase fails, any characters that passed the former level cap will be locked for play. You must complete the upgrade in order to unlock those characters.
For example, if you upgrade from World of Warcraft (level cap 90) to Warlords of Draenor (level cap 100), you might level a character to 91 before the purchase completes. If that purchase gets declined, your level 91 character will be locked until the license is successfully upgraded to Warlords of Draenor.