If you mean the fan in the furnace works fine, but there’s no ignition, it implies that the sailswitch may not be closing to allow the gas valve to open. This can be because the fan isn’t blowing strongly enough to push the sail, and hints that your batteries aren’t fully charged.
Memory is very dim, but isn’t there a gas shutoff in the line going into the valve just outside the furnace box? Check that the tech didn’t shut it for some reason. If you can hear the ignitor “snapping” but no flame, that’s another valve-off clue. It could also be the ignition points are fouled and not sparking across (so there’s no snapping sound), and need cleaning/alignment. Or as previously noted, a fouled nozzle may not be letting gas through to ignition, or wasps may have built a nest in the outside intake or exhaust restricting adequate burner air flow, again perhaps handcuffing the gas valve solenoid.
Also, are you being patient enough... my wife used to gripe when the furnace was first turned on cuz on some models it can take up to several minutes of blowing cold air before the various delay switches allow voltage through to the gas valve solenoid.
If you Google or YouTube “suburban furnace wiring diagram“ you’ll find more than you really want, but including perhaps insightful videos.
Joel