I had a similar setup(hookup) on my VTH215.
I was able sync the tv/soundbar with the directv remote.
The tv would never turn on after the directv box went on unless I hit the volume button.
I contacted Vizio. They said that the soundbar went into a "sleep mode" until come activity
occurred, such a adjusting the volume, since using the arc/hdmi hook up, everything pasted thru
the sound bar).
Maybe you are having a similar "sleep mode" situation when there is no activity.
On a side note my vht 215 stopped working last month,(could not change settings) 13 mounts after my purchase.
It was covered by an extended warranty. Could not be fixed. The warranty company cut me a check for the original
amount plus tax. I'm ordering the zvox z-base 555 next week to replace it. Btw I loved the 215. just want to try
something different, and can return in 30 days if not happy.
Hope the info helped..