Several users are reporting the same problem I'm seeing.
http://forums.slimdevices.com/showthread.php?97568-MOG-Stopped-Working/page2

1. Running LMS 7.7.2, on both win7 and fedora (vortexbox) PCs.
2. Paid MOG account that was working perfectly
3. Problem:  When navigating to MOG, it will find Albums, artists, favorites, but then when selecting, it will seem to search for a long period. Once items are found, selecting to play will eventually produce a 504 - timeout or gateway error, but then the next song in the list will begin playing and the rest of the album may play just fine. Then first song that was skipped might play if tried again.  All very hit and miss.

It seems as if the Logitech MOG app is having trouble making the initial "handshake" with MOG.