Cold convector on second floor

Michael_31

We have a hot water system with convectors, I can't tell if it 2 pipe but I think so. I turn u the thermostat and all rooms warm up except a second floor bedroom furthest from the Boiler. No matter how hot the rest of the house gets, that convector and it's feed pipes are ice cold. Basement has finished ceiling so I can't see any main line going to that bedroom. When I try opening the vent on the bedroom convector, I get a tiny bit of air then water, so I can't imagine it's an air problem.

I have no access to any feed pipes at the convector, I can't tell if I have diverters in place. I tried to understand the article on that, seems to make sense, but can't relate it to my problem.

How can I get heat to this bedroom?