let me guess you got it from home depot. Anyway be careful when you are talking CFL's and you say 300W.. You should be clear if that is the actual wattage or the incadescent equivilent which im sure that is an equivilent value. Anyway i have A 300W light and i bought a 10.5 Inch reflective hood and when i screw the bulb in it doesnt work. Try to unscrew the cone itself and if it has its own socket try the light in the socket. Most likely the bulb is too big to be screw far enough into the socket to make proper contact.. i returned mine