This error occurs when the Blizzard Launcher can't read recently downloaded patch files. This may be caused by hard drive corruption, missing game files, or corrupt Blizzard Agent files. Follow the steps below to resolve the issue.
If you're using a wireless connection, optimize your internet connection to rule out a connection issue.
Run ScanDisk and defragment your hard drive to try to repair any bad sectors.
Note: Do not defragment a Solid State Drive (SSD).
Delete the Battle.net Tools folder to automatically rebuild outdated or corrupt files.
Repair Disk Permissions to resolve any permission conflicts with logon modules.