You have to find someone that can build a connection to him. My son's best therapist played minecraft and roblox with him. Seems odd but as they were playing he would talk. Eventually she was able to move him off the games and onto walks. And then finally into the office for what we think of as traditional therapy. Even in the office though there was always another activity that he could do in addition to talking--puzzles, figits, board games. He was 7 when he started with her.