Why are the pipes to the radiator always cold in one room?

Hello people of Warsaw! There is a general heating system in the apartment I live in. I have an issue that in of the rooms of my apartment, the pipes to the radiator (kaloryfer) is always cold when I touch it even during the very cold days. I can hear the water flow when I adjust the valve of the radiator but since the water and the pipes are very cold, the radiator doesn't get warm. In the other rooms however, the radiators are working very well and when I touch the pipes they are hot. What can be the reason or is there a way to make this water hot?