The "obvious" thing to me, is to make sure each box is rebooted in turn, however...
Is the lack of comms between the TiVo & your V6, both-ways? So the V6 can't view TiVo, and the TiVo can't view V6?
The TiVo connects differently to the V6 and it's been a while, but I recollect the Network Connections screen (Home > Help & Settings > Settings > Network) should list the Ethernet (for multiroom) & in-built modem (for OnDemand & streaming) separately.. what do you see?
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