ASD friend is missing in action and I am concerned

I have a friend that I met online who has ASD. We are in different geographic locations (me = USA, him = UK), but we were messaging each other throughout the day, almost every day for the past 6 or 7 months. I know he has been stressed with his job and other people in his immediate world, lately. He warned me that he was considering deactivating his social media for a while because it was stressing him out, and said that he didn't want me to panic. It has been almost 4 weeks, so far, that he has been gone. I have no other way to communicate with him. I am very worried, as I want to be sure that he is ok. I, of course feel unclear about whether he wants to talk to me anymore, also. Could this be due to a "shutdown" or "burnout" on his part? From other things I read, that seems to make sense. I guess I just need some advice on what to DO. I know I should be patient, and I'm not mad at him or anything. I just want to understand what's happening and I need some guidance on how I can manage myself until/if he returns. Any insight would help at this point. Thank you in advance.