ive done that too. cut off and lugs and then trimmed it down in size too. even tried another bulb but no joy
what i may do is fit it all and see if there is current to the bulb holder as i may have the +/- the wrong way around and i'm guessing that this could be the cause. The wiring was put in place many many months ago when i replaced the bumper.
unless your using leds it wont mater what way round it should be
you are putting it in reverse arnt you ?