Hi Louise,
If the powerlines are disconnected neither box is visible to the other immediately.changed the primary powerline plug to a new 500Mbps unit, which hasn't helped much. I will try and explain the setup and what happens in a little more detail. The V6 box is connected directly to the hub and is named "Special Room". The hub is also connected directly to the TV's Ethernet socket and to the primary 500Mbps powerline plug. The old Tivo box is in the adjacent room and is named "Dining Room" The old Tivo box cannot be connected wirelessly, so is dependent on the powerline 200Mbps Ethernet connection.
When they are both connected via the powerline plugs Dining Room can see Special Room and all the recorded programmes are accessible. However, Special Room sees Dining Room, but it is greyed out. This does not differ if I connect Special Room wirelessly.
In answer to your questions, by looking into the router settings the V6 box is running on 2.4g when connected wirelessly and the speed is good for TV service.
My current thinking is that the problem probably lies in the powerline connection, despite all being well at first.
Many thanks,
Andy