'Ok Google' doesn't work on LG G3

Recently the "Ok Google" feature no longer works on my LG G3, unless I factory reset my settings. But after a few hours it stops working again even if I don't change any of my settings back. I even upgraded my phone to Lollipop, but that didn't help either. Also, I tried reprogramming my voice back into my phone via "Google settings", but it won't pick up my voice either. So long story short the only way I can get it to pick up my voice is by clicking the microphone.