based on what was mentioned previously about brake cleaner, you ONLY use that to verify if the engine is firing and will run. NEVER use an excessive amount to make the engine run continuously because of the afore mentioned noxious gasses it produces. If you've ever done this you will know, the smell is bad and burns your eyes and sinus's, ie: it IS bad for you... so don't load up the intake with it ;o) If you have some ether (starting fluid) use that, it takes less and the gasses are non existent pretty much.
Now with that said, once you verify the engine will fire off using a starting aid you've verified that the electrical part is good.
If you do not get any ignition and the engine will not fire off then start checking the coil, the wires, wire terminal ends, cap, rotor, pickup unit inside the distributor, voltage to the distributor, neutral safety switch, etc.

In the event the ignition is working ok, Concentrate on the fuel system, fuel lock off, converter, line filter, mixer. The most common components that cause no run condition are the converter or the fuel lock off valve.
-verify that the converter is getting lp gas, crack the input line at the converter and turn on the key for a second, it should let out a burst of gas (it will be liquid so keep clear of it as it will burn/freeze you. If you get that burst of fuel that verifies that the lock off, tank valve and any other component from the tank are good.
-Then if all is verified before the converter you need to check the output of the converter, you can take the hose off at the input line on the mixer, energize the system, even crank of the engine for a second or two and monitor the hose you removed at the mixer, you should get vapor gas out of it. It won't be a huge amount but you should hear and smell lp gas coming out of it. If you don't think the converter is most likely bad. If you do then move on to the mixer.
-take the top off the mixer and check the diaphragm for splits , cracks and check the center button and make sure the assy is clean, especially around the button area where it seals off. Also check down inside the throat of the mixer body and use some carb cleaner to clean it out.

If you follow these instructions you should be able to determine where the issue is.