Did you put afterrun oil in the engine before laying it up?
Have you replaced the glo-plug with a new one?
Is the fuel you are using new?
Is the glo-ignitor charged fully?
Is the fuel tubing new?
Have you replaced the fuel filter?
Are the gaskets that seal the engine in good shape still?
4-5 years of a lay up without proper preps can cause any number of problems. Each of the questions I asked above are trouble spots. Old fuel tubing can have leaks from rot. Old glo-plugs corrode and cease to work. Old gaskets rot. Fuel filters develop leaks if sealed with an o-ring and said o-ring is rotten. There are a number of things that can be the root of your problem.
If the stuff above has been replaced with new or brought up to date or proven to be in good enough condition to run, I would then recommend resetting the needles on the engine to factory presets and try to start it from there, and then retune once you get it running.