Radiator Fault? Hi, I've Just bought a moved into a new house and two...

Hi, I've Just bought a moved into a new house and two of the radiators contained by the upstairs bedrooms arent working. The house use's a combi boiler (about 4 years old) and i have already blead the radiators neither of them have air surrounded by.

Any ideas of the problem and how to fix them.

Thanks contained by advance