i know this is bad but I have some mental issues sometimes and I out of the blue end up I ignoring all my friends for days and sometimes weeks. it really isn't personal but I almost feel bad for the other person for talking to me lol. It's really irrational and its a bad habit but yeah I end up ignoring them despite having a good conversation.
I think its in part because I'm scared of disappointing them because I think they have certain expectations from me that I can't meet.
I'm not too sure but this couuuld be what's happening with him as well.