I have a liitle problem with Preston Garvey.

At the beggining of the game, I choose Preston as a companion, and later , I choose another companion and left Preston in Sanctuary.

I don't know that the characters give you perks, and when I gain the first one, I continue with the other characters, until I choose Preston. I can't talk to him. Preston always give me mission of the Minuteman, but I can't talk to him to join me.

The missions that I have done is in the Principal Story (until de Search of the Intitute in the Memory), The first one of the Brotherhood (And I say to Danse, maybe I join later), and the Minutmen (until I reclaim the Castle), and severals secundarys.

I don't know is this is a bug or I have done something wrong.

I know only this: Preston may become unavailable to recruit before the siege on the Castle. If the Castle is then retaken, he will no longer engage in dialogue past a greeting or a settlement quest.

That should be a glitch. There is not fix about that, except reloading a save and make other choices.

It's not quite clear to me from your post whether you've reclaimed the castle or just done everything up to it.

I had a similar problem, where Preston would only give me radiant missions and ask me to retake the castle, and it was resolved when I went ahead and retook the castle. He just sort of got stuck on that dialogue and wouldn't go to the "travel with me" dialogue.