It's a more common issue than people may think. I don't think I had an orgasm until I was 19. And then I could only do it when I was solo.
I couldn't orgasm in front of another person until I was like 22. By the time I got to my mid-20s I could orgasm anytime, anywhere, and in front of anyone LoL. For me, it just took experience and time. I didn't really see a therapist or anything like that.
However, there are lots of medical/physical reasons that could cause it. If I were him, I'd get checked by a medical doctor, just to make sure it's not something that could easily be remedied or worsen if left untreated. It's nice that you care about him enough to be concerned.