Hey! How long has it been since the last time he replied? If it has been more than a month I would talk to him in a casual way. I would write telling him I hope he’s okay and asking what happened. Just in order to move on with your life mainly because if he didn’t appreciate the opportunity he had with you then he certainly is not meant for you right now. Just some of my thoughts! I do think it is necessary to have time for yourself and understand the reasons why it didn’t work out. Everything happens for a reason!