Usually because he is angry at her, is no longer interested, or has a new girlfriend. You could try asking him, but he may not tell you, particularly if the reason is because he found a new girlfriend. In the U.S. we call it "ghosting." It means that you have been dating someone and they suddenly stop calling, texting, or visiting you. They don't respond when you try to contact them. They cut off all communication, but don't tell you why. Once someone ghosts you, it almost always mean that the relationship is over.

If a man asked for learning friendship and girl does not accept then a man ignored her.