This error means Battle.net Agent (the process that installs and patches our games) couldn't stream necessary files.
Information for troubleshooting Call of Duty: Vanguard launch issues
Location of Diablo III crafting materials
Game crashes or doesn't load after pressing "Play" in the Battle.net app or crashes mid-game
Troubleshooting your security programs can resolve issues preventing you from installing or using Blizzard software.
Something went wrong while trying to download a file. Please try again.
Something went wrong while trying to launch the game. Please make sure it's installed and updated, then try again.