I have two Series-2 Dual Tuner TIVOs. They have both been hardwired to my network router for over a year, and I have never had trouble transferring recorded programs in either direction ("Multi-Room Viewing"). However, recently "TiVo 2" is no longer visible in the now playing list on "TiVo 1". (The opposite direction is still OK, and I can see #1 from #2, transfer from #1 to #2, and play these immediately on #2.)

How would I start troubleshooting this problem? Does my PC need to be booted and logged on for this to work?

What are "TiVo Server", "TiVo Beacon" and do they affect this?

Notably, my TiVo desktop seems intermittently unable to "see" either TiVo. Does this matter?