My network port in my bedroom deos not work

Find where the other ends of those Ethernet cables are. Check a bedroom closet for a networking panel. Most likely the other ends are not terminated. Even if they are, they would need to be connected to the gateway or a switch connected to the gateway. 

What room is the gateway located in? What model gateway?

Picture of an apartment network panel with the ONT in it. 

Thanks for the reply @browndk26 ! 

My gateway is in a wardrobe in the room located on the opposite side of the apartment where the panel is in. That is also why WIFI can get unstable when I using my PC.

The gateway modal is bgw320 500

I don't have an idea where the ends of those Ethernet cables are

If you could find the ends of the Ethernet cables then you could use a continuity tester and identify which cable was which and where it goes.

Essentially the apartment complex is responsible for the wiring between rooms, not AT&T.   They'll refer you to your ISP to avoid ownership, but that's crap: it's their baby.  Ask them how it's suppose to be set up.

You could call Att and have them redo the installation and place the gateway in the panel. Then the gateway could connect to the legrand switch and hopefully get all the Ethernet ports in the apartment live. Wi-Fi may suffer with the gateway in the panel. 

Before you do call Att, get a long Ethernet cable. Run it through the apartment and connect one end to the gateway and the other to the switch. See if that gets service to all the Ethernet ports. You will have to experiment with different ports to see what works. Of course I’m assuming all the ports in the rooms are terminated. 

Is the red Ethernet connected to anything?

You can also ask neighbors and apartment maintenance how other units are set up. 

Edit, it’s also possible you could connect the gateway to the port in the room it is in now, back to that switch in the panel and get service to all the other Ethernet ports. 

Do the apartments have an agreement that only Att provides internet service to the complex?

Thanks for all the reply! Will check with the apartment to see if they can help

@browndk26 The red cable is connected to the gateway

So is that the gateway at the very bottom of the picture? If yes, why did you say it is in a room on the opposite side of the apartment?

@browndk26 oh I mean the PC is on the opposite side lol

Post a picture of the back of your gateway and a picture of the legrand device that your Ethernet cables connect to. A new install should have fiber direct to the gateway. I’d like to know what port that red cable is connected to on the gateway and legrand device.  No need for a tech to come again. You can probably get that outlet the pc connected to live. 

@browndk26 Sure