the obvious one is: switch it off and on again.
what is the exact message - it the V6 complaining about V6 - hub link or v6 via white coax to Virgin link or is it being annoyingly vague ?
you say tivo can see V6 ( but not vice versa) so can you actually playback a v6 recording on the Tivo
is your powerline setup apparently working i.e. go you have green lights at each end where they normally appear, and flashing lights indicating data transfer
do you have any other device you can connect via powerline as a powerline test ?