02 cadillac sts, dvd head unit problem

info: 2002 cadillac sts seville head unit: pioneer avh-p3100 problem: the unit goes into mute after 10 mins of watching video while parked, and when i press the button to un-mute, nothing happens its like the button doesn't even work. Also trying to use the volume button up or down does not take it out of mute status, video still plays though. this was a self install, did i do the park brake sensor wrong? I can't tell, its confusing because the video still plays, i can access all the video functions but no sound...also its in demo mode, is that why? how do i take it off demo? thks for ur help fella'sNitin Nelapudi

with the key on, HOLD the SRC button till the unit shuts off. Touch the screen to bring up a menu, From there scroll till you see the DEMO option.