Macbook pro not going to sleep

I have a macbook pro retina 2013 I think,

It doesn´t go to sleep when I press the sleep button.

I have noticed that it goes to sleep if I unplug the thunderbolt cable

that is connected to the internet.

But I don´t want to unplug this all the time I want it to go to sleep.

What should I do?

I have also tried smc reset and NVRAM reset.