Air, fuel, spark and compression. Good places to start. Find out which you are lacking.
SLOWLY hit the primer. Does it fill up the bulb with fuel? Don't smash it like you are trying to draw blood. It will bring more air into the carb. Primer bulb should draw mixed fuel from the tank sending it to the carb. Overflow hose from carb goes back to the tank. Bulb should be darn near full of fuel.
New Stihl carb with the same part number as you replaced? Or some Chi-na' carb that you saved a whole bunch of money on?
Could have a cracked fuel line, clogged fuel filter, dead spark plug, plugged up U.S Forestry spark arrestor screen and maybe some seals. Ignition coil, sheared flywheel key........