Have you tried plugging a keyboard and mouse into the USB ports, re-doing a fresh image on the MicroSD card and trying again with the Network cable attached. That did it for me.
If you have a Keyboard and mouse plugged in, try it with them unplugged, it seems like a timing issue and you just have to change enough to make it work.
I am also trying to get a multi-room system running. It is a bit frustrating as I think it will work, it just isn’t quote as smooth as it should be..