BLZBNTBNU00000003

The Battle.net desktop app failed to communicate with the Battle.net Update Agent, which is required to install, update, launch, and uninstall Battle.net games.

1. Update your drivers and operating system to resolve any compatibility issues.
2. Uninstalling and reinstalling the Battle.net App may resolve rare launcher issues.
3. Run a security scan to remove any viruses or malware infections.
4. Update or temporarily uninstall any security programs, which may mistakenly identify the login module as a security threat.
5. Try creating a new administrator account (Windows only) to resolve permissions issues.

Tried everything here?

If the previous troubleshooting steps didn't resolve the problem, you can ask the Blizzard player community for help on the tech support forums (if available) or other community gaming sites. Local computer or network technicians may also be able to help if you've exhausted all other resources.