I''m sorry for your situation, and his. Everybody wants to feel connected, heard, loved. If communication is blocked, both of you suffer.
If he will listen to you, then apologize vulnerably without blame: you are empowered to do your part to make it safer for him to take down his walls of protection. "I am sorry we aren''t talking effectively and sorry for my part in it."
Then ask, "What have I done or said that makes it difficult for you to open up to me?" And if he will stick his neck out and tell you, then listen non-defensively, and ask, "What else?"
Check out to see if you understand his concerns, then do something to make him glad he told you the truth. What you''re seeking is change in the relationship, and that will take courage for both of you.
Your goal is to listen so well that he discovers more about himself and your relationship as he discloses to you his perceptions. He will find it rewarding to be heard, understood, and feel felt.
I''m teaching a workshop on this next month, and afterward could send you more information or even a video if that would help.