The furnace and central air conditioner both run but no air is coming out of the ducts at all? changed filters on it and still not working. Any idea of what to check?

you say the furnace is working,,,,are you sure the indoor blower is working?if it was you would be getting air,,,,,,take a look to see if there might be a lot of ice build up,where the 2 copper lines go into the furnace coming from outside,,,if there is turn everything off and give it time to thaw out,,,,,let us know