I have a quest called "Defend Abernathy Farm" the only objective is to "talk to preston garvey" but it is grayed out already. I talk to him but he doesn't say anything about it, just normal chat. Also, I can't turn the quest off, it's stuck on!

ive been to orther areas and its still the same ive reloaded and its still there ive slept for 24 hours and still there.

ive also been to the farm and northing happens

how do you get it to work?