The Blizzard app cannot access required login files to connect to the Blizzard service.
Run the game in Administrator Mode to address many installation, patching, networking, and start-up errors.
- If the game or the Blizzard app is set to always run as administrator or run in compatibility mode, this may cause launching errors. Right-click the game or the Blizzard desktop app, select Properties > Compatibility, and uncheck Run this program in compatibility mode and Run this program as an administrator.
Delete the Battle.net Tools folder to automatically rebuild outdated or corrupt files.