No, not much progress being made here.
I've de-authorized & re-authorized a number of times & still get the same message. I can play/stream these tunes from my laptop & the album cover art, etc. shows up on the TV, but cannot play them from ATV.
One thing I've noticed is that my laptop (a MacBook Pro), which is also in my living room, responds to my clicks on the remote, even though I'm aiming it at the ATV in the opposite direction. So it's duplicating, essentially, what I'm seeing on the screen of the ATV. It just occurred to me that maybe there's a conflict there -- I'm at the office right now, so I'll try controlling the ATV with the laptop turned off when I get home.
Another thread of mine on the discussion board that isn't going anywhere either is concerning YouTube, which is also not working on this new ATV. It just says that no content is available and that it can't connect with YouTube at the moment & to try again later. Entering my username & password for youtube is refused also. Not trying to cross-post here, but mention it in the unlikely case the two are related.