Gas furnace fails to fire up and provide heat
Sounds like the furnace may have failed the first diagnostic test for the draft inducer.
If the system doesn't detect a positive pressure to the pressure switch after the inducer motor starts, it won't let the burner igniter operate and throws a 4 flash code.
Sometimes the tech just needs to remove the vacuum hose from it and clean out any debris that may be plugging up the hole or the hose and put the hose back on and it will run.