First of all you should probably make sure that Windows 8 Global settings is not configured to use a proxy server (unless of course, for some strange unknown reason that is a conditions of your connection, which I doubt). You'll find that in PC Settings, Network, Proxy. Just slide everything to "Off". See attachment
Then check your individual browser(s) (which ever one you are using or probably all of them) is not using any proxy settings
You can Google proxy settings for individual browsers and just use that information to uncheck / turn off any reference to a proxy server.