I like a girl, but suddenly she doesn’t reply to my text messages. Why? . .

Maybe she misunderstood you about something, you can ask her good friends in a subtle way; it is also possible that she just has no feelings for you and no longer wants to be friends with you; or she is very busy. I have encountered something annoying and I have no time to care about you; you can try to calm down for a few days and gradually send her less text messages to see if she will react