I am in a similar boat - got my VM TV V6 yesterday evening.
I uninstalled my old VM box, which was working fine. Activated the new box and installed the new box. All was going well, I got through the to welcome screen. I forgot to plug in the ethernet cable, so the screen came up to tell me that. The box then spent a while updating, so I just left it over night.
In the morning, all was well. The box had finished updating and then went to play TV. I got the VM channel list overlay and sound of the channel, but no picture.
Now, when I restart the box, I get the starting up graphics and about a second or two of the channel graphics, but no TV picture. The graphics then dissapear after a second, it the sound continuing.
I have changed all the cables. I have switched TVs. I have checked the Denon is running the latest software. I have checked the TV6 is fully updated. I have reset the TV6 box. I have tried to force a handshake by pulling out the HDMI cable into the Denon. I have unplugged the router, amp and TV6 box. I have double checked the HDMIs are going into the ARC channel HDMI on the TV(s). The TV6 works if I attach directly to the TV.
The Denon is completely capable of running hdcp 2.2, so I don't really know what else to do. No doubt, Virgin will say it is not their issue.