According to your last message though, you were mad that he was liking another girl’s pictures on Instagram (which initiated you sending another message).

From the outside, this reads like jealousy. If there is no longing in your heart for something more, then why would his social media habits cause you to be upset? It may be worth reflecting on that to understand your motivations.

I don’t think anyone can force someone else to respond to them. He has communicated boundaries. You may continue to hurt yourself and the prospects of a friendship by not respecting them. In order to maintain a respectful friendship, I feel you need to give some space and let him make the next move. You may be unintentionally overwhelming him and pressuring him.