The girl I like doesn't return my messages.

There are several possibilities for a girl you like not to return your text messages:

1. You like her, she doesn't like you, and she doesn't reply to the message because she wants you to back down.

2. I was busy with other things when I saw your news, so I didn't have time to reply to you, and I forgot your news when I had time.

The girl didn't know how to reply to your message, so she put it on hold for the time being.

Maybe there are other possibilities, you can also list them yourself, then rule them out one by one, and then decide the next step after determining the specific reasons.