I have two V6, connected by power-link ; 1 in the "office" and 1 "living room".
I can see the "living room" v6 from the "office" V6 and access all the recordings, however I can not see the "office" V6 recordings from the "living room" V6, It has an "!" against "Office" in my other TIVOs and when selected comes up with error code C423.
This has been refuted by some on here but seems to work for your situation.. on the one with the ! go to Home> help & settings> settings> devices> network remote control> set to 'allow' (may need to do on both boxes)
Some on here say that has nothing to do with viewing other boxes, but I have seen 3 users on here say it fixed their issue with the boxes not communication.