Standalone patches are downloaded outside of the game launcher or the Battle.net desktop app.
This error means Battle.net Agent (the process that installs and patches our games) couldn't stream necessary files.
How to resolve issues with slow patch downloads
This error occurs when you have connected to our patch server but you cannot download patch information.
How to resolve this issue when installing or updating a game
Instructions on how and where to download our games
What to do if you can't get the Battle.net App installer downloaded correctly.
Something went wrong while trying to install. Please try again.