No Heat from Panel Radiator

I recently installed a Radson Panel Radiator, to replace a free standing cast iron radiator during a bathroom remodel. The radiator worked for at least five days during cold weather, then all of a sudden, no heat. The existing system was an old gravity system converted to forced hot water with pumps in the return, with a 3'' main and 1'' feeds off the top which I adapted onto. I spoke with the rep and said that this particular set up wouldnt effect the radiator and the water should pull through, which it did. Now there is no heat unless I continue to bleed water from the radiator. Will contact the rep again tomm. Looking for any ideas. I apoligize in advance for spelling and grammar.