Quick sync wont work

I cant get quick sync to work for the life of me. ive tried youtube tutorials and failed as well. Im currently running a tripple monitor setup with two monitors hooked up to my GTX 770 and one to my asus motherboard. ive no problem having the HD4000 graphics driving a monitor (ive tried disconnecting that monitor as well) yet it still wont work in sony vegas. it used to work and now nothing. Ive gone into my bios and enabled Igpu and all that jaz. anyone have any idea what could be the issue? 

Too broad of a desc.  I don't really understand what you're doing, or what you've tried.