I sent the words Happy Birthday to my ex-boyfriend. He didn't reply to anything. Why? What is his psychology of not returning?

Honey, I can't say anything else. I can only say that people are out of memory and there is nothing to miss. I only despise you. Because that has become a distant memory, he won't pull you into his present. After all, he already has a girlfriend. He may be busy, or he may deliberately avoid you. What's more, you are redundant. Maybe your behavior is just mean to him (I mean no harm, just the truth). After all, yesterday has passed. Do what you should do today and plan a better tomorrow. This is what you should do. No matter how he is, your blessing has come to you. I wish you happiness.