There's a problem with the connection to the Blizzard servers.

Before you can connect to the game servers, you must add a phone number to this account.

Information on error BLZAPPBTS0000F

Troubleshooting steps to resolve voice chat problems in World of Warcraft

Troubleshooting step for connection-related problems on Windows.

Information about the error "Please select a different realm" when attempting to transfer or faction change a WoW character.

Information to troubleshoot connection, latency, or UI issues which may prevent your character from changing zones

How to troubleshoot connection issues between Battle.net and Steam

Information on error BLZ51900001

Troubleshooting game or Battle.net services connection error BLZBNTAGT00000BB8