LS990 Update Issues topic

hello everybody, quick question and i apologize in advance if this has been covered somewhere else or for just being a dumb question in general; I have the LG G3 from sprint and a little over a month ago i had a friend root my phone and convert it back to stock android. In anticipation for android 5.0 I removed the root. for over the past week I have been spamming the update software button and still have no lollipop. one of my good friends told me that by converting back to stock android i probably disabled the over the air updates. I was wondering about how to go about getting the updates, i have seen some posts suggesting to use the lg flash tool but I did not really comprehend how to use it. sorry if this is something stupid still really new to android.

thanks