Xilni

 You had raider settlements in the commonwealth? If yes, then sure - Preston won't talk with you. If you "convert" a settlement to a raider one this will lock up Preston.  Yes but I did all of nuka world and Open Seasons before meeting Preston so he never even commented on it. I guess there was some behind the scenes variable blocking the dialogue with the raider settlements still up but not dialogue to react to that particular situation. After wiping out the settlements and getting rid of the raider flags though it worked perfectly. EDIT: typo

So didn't end up being a companion problem. Followed this advice and it worked. Turns out it's not enough to complete Open Season, you need to reverse the raider settlements and repopulate the settlements.

I've been getting the same issue relating to Preston Garvey's dialog going blank after "Anyway, I'm glad you're here" while trying to turn in When Freedom Calls. I tried this command but then when I speak to him he still tries to have that same conversation with me and it once again gets stuck with the blank conversation. I'm worried it may have to do with the fact that I completed Nuka World (all the park, 8 raider settlements, open season), but I was under the impression if I completed Open Season before even meeting Preston that it wouldn't be an issue with dealing with him.