Blocking a legitimate website

you are blocking this web site https://sso.uned.es/sso/index.aspx what is the portal to access my virtual classes on my PC it works with a VPN and with my Cell phone provider. When I try to log into my portal I get this message ERR_CONNECTION_TIMED_OUT

This is a Xfinity problem and need to get it solve as late as tomorrow since I need access to my clases

Thanks