So me and a friend are trying to start a co op game. I sent him a key he downloaded the trial game and whenever he try's to join the game he gets a message saying the feature is unavailable. Anyone else run into this?

No sorry. Yesterday I played coop with a friend who ALSO owned the game. At first I couldnt join his game, I forgot what the error message was. But then it allowed him to join me. And later I could join him fine too. I think we used the PS4 system level invites to do it.

I am a bit disappointed how little progress carries over the player joining (Hurk). You can earn money, karma, and experience which carries back over. But doing side quests, taking outposts, and radio towers does not carry over to Hurk's single player progress. That said, I love the wide breadth of things you can do together, very fun.