cannot install WPMUDEV dashboard

hi I'm receiving this error "GnuTLS recv error (-9): A TLS packet with unexpected length was received". when trying to login to the WPMUDEV dashboard after installing the plugin.

I contacted my host TPP and they said "unfortunately our server does not allow connections to external servers unless they go through a proxy server" and directed me to the following page but couldn't give me advice as to where this code show be placed -