When my H first moved out, he would come over at least once a week and stay for about an hour. As time went on he was here less and less. He looked horrible, had those "dead eyes." Soon after that he would disappear for 6 or 7 weeks and not even realise it had been that long. This went on for a long time. At first I would bug him by calling him. That didn't work, so I forced myself not to call or contact him. I left him alone and let him work through his problems while I worked on myself.
I did notice that my h was really, really depressed. He even talked about taking his life. I was worried and suggested that he seek C. Then he would tell me that there wasn't anything wrong with him. I could see it and so could everyone else. Someone even told him that he needed to be committed. What I am getting at is no one can force them to get C. My h finally did get C after people at work were noticing the changes in him. He was good at hiding it for a long time.
It seems like when the world is crashing around them is when they reach out and go to C. At least that is what happened in my case.
Be patient and be there for him when it starts getting rough. Be the light house.