Unplug from power and all HDMI and USB connections, wait a few minutes and try again.
Woke up today to TV that wouldn't turn on, finally it did turn on with Directv remote. 4 Android icons on screen with black background. Will NOT respond to any input from either Sony or Directv remotes. If this TV does do updates it warns me first, and when I shut it down last night there was no notification of impending update. Now stuck with 4 icons on black background.