Steamcmd Troubles, keep getting error messages.

Hello members of FacePunch :D!

                     I seem to be having troubles with Steamcmd and setting up a Garrysmod server. When i start up Steamcmd and i type in all the information like

Login Anonymous
Force_install_dir C:\Users\*Username*\Documents\steamcmd
app_update 4020 validate

Then it starts downloading the content it maybe gets around half way then ends giving me an error message of…

Error! App '4020' state is 0x402 after update job. <- Heres a picture of what i mean.