Multiple ethernet ports in multiple rooms

Hi,

I have 2 ethernet ports in 2 rooms that both run to the garage where the ONT box is. The one in the living room is connected to the router. I tried to plug my laptop into the ethernet port upstairs but it is not picking up anything. I looked at the connection in the garage and it appears one of the ethernet cables isnt plugged into anything. Is there any way I can get connection upstairs via the ethernet port? 

Thanks in advance