I do not think water is going into the boiler to be heated
The furnace has a cold water inlet valve it should be on but if it is off then you should find it. Follow the cold water lines from the meter or the well pump if you need to go that far back and make sure the valves along the way to the furnace are open carefun not turn on an outside valve if it cold outside. When you find it if it's off turn it on then you have to find all the bleeders in your radiators and open them to let the air out. Hope this helps. If that's the problem
Professional intervention is required, Boilers/furnaces are NOT DIY items. To many dangers, ranging from CO gas leaks to explosion to the ruining the efficiency. Consult your fuel supplier for qualified personnel (they probably have a maintenance department, if not they'll send you in the right direction)
1. Check the water inlet valve, it should be open 2. If water supply valve is open, but water does not enter, the vessel may have an air block, so, lift the safety valve up, to release air pressure. Hold the lever up till you get the water flowing. 3. If this does not work, stay away (mind your safety) from boiler and call mechanic to inspect your boiler. It may be choked with scale accumulated at the water inlet. 4. If the boiler has been energized, do not do anything until you have proper Personal Protective equipment on your body.
