No roast from 1 radiator? Oil fired boiler 3 floor multi family house . All strike iron...

Oil fired boiler 3 floor multi family house . All strike iron radiators on 1 zone . Only 1 radiator is not working .Bled the integral house starting from bottom to top . All radiators except for for 1 on the 1 st floor . Bled again still cold . Water is flowing out of radiator .
Pressure in boiler is at 20 LBS. What can the problem be ?
A tool used contained by floppy doors is...
Answers:    if this heated finishing year ok
there might be a spigot turned off at the radiator supply or return or if it's a mono flow system the inflow could be plugged up