Any electronic switch or dimmer that doesn't have a neutral connection relies on current flowing through the bulb to complete the circuit. That wasn't a big deal with the filament on an incandescent bulb--a watt or two wasn't enough to heat up the filament enough to make it light up. But with a CFL or LED bulb either the bulb lights erratically while the switch is off or else the whole thing doesn't work.
That's why NEC now requires a neutral in the switch box. New electronic switches designed with a neutral connection (not to be confused with the ground screw!) will use the neutral to complete the circuit instead of going through the bulb.
When a neutral is not available, sticking with an incandescent bulb may be the best choice.
If this light is in a closet and on a motion sensor switch, presumably it won’t be on that many minutes per day. Was there another concern besides energy savings? If the bulb is hard to get to, this could be a good application for a “heavy duty” or “long life” bulb so you don’t have to change it as often.
Or use an LED bulb but loose the motion senesor switch and just use an old fashioned toggle switch--but then you do need to remember to turn it off yourself!
