I am not sure why you want to be friends if he isn’t supportive of you?

My take on all this is that he moved on, isn’t longer interested hence isnt checking your messages. Contacting him further and asking why he isn’t opening your messages is putting him on a spot. Personally I’d follow his lead and move onas well. I am not sure why you want him to keep communicating with you? Typically if you go on few dates and it’s not working out, there is no need to continue communicating.