BLZBNTAGT00000840

The Battle.net Update Agent couldn't modify necessary files on your hard drive. This usually happens when the required files are locked or in use by another program. Follow the steps below to resolve the issue.

1. Restart your computer to ensure that a part of the game is not open in the background.
2. Run the repair tool to repair any damaged game files.
3. Update or temporarily uninstall any security programs, which may mistakenly identify the Battle.net application as a security threat.
4. Try creating a new administrator account to resolve permissions issues.
5. Uninstalling and reinstalling the Battle.net App may resolve rare launcher issues.
6. Uninstall and reinstall your game.