I had an argument with a friend. As I felt badly about this, I texted him and apologized. I never heard back from him. I am now angry with him about ignoring me. What else might I have done to make this better?
Please realize that you are not responsible for his behavior. You did a kind act in apologizing. You might wait some more because his forgiving is not necessarily on your timeline for this. He simply may need more time. Yet, how he responds ultimately is up to him. If he never responds, then I agree with you: You may have to forgive him for that. Also, you should go in peace knowing that you have done what you can to renew the friendship.
For additional information, see Why Forgive?