If you get this error when you try to install WSUS in a server it does mean or you have not an internet connection to download the important files or you you have set up group policy settings for Windows Update. If your server is a member of a domain controller then check the update policy settings in Domain controller which is in Group Policies\Computer Policies\Windows Components\Windows Update.
Change the specified update address to Not configured or Disabled. And Change Client side targeting to not configured.
Then enter to server which you want to set up WSUS in. Open Command Prompt (CMD)
and type gpupdate and click enter. The policy from your domain controller will be updated. And try to set up WSUS.