I have this model and it stopped working on me. Turns out it just needed a cleaning and oiling since it was jammed up with hair bits.
Try removing the trimmer completely and sliding it back in. You do this by first removing the blade cover at the top of the electric razor since otherwise it gets in the way. Then push the trimmer up and keep pushing until it slides right out. Examine it closely for any broken parts, clean out all hair and debris, and slide it back in. You have to line up the back of the trimmer at the right spot to slide it into the tracks. If it is broken and you can't fix it, there are at least two online retailers as of April 2016 that were selling the trimmer piece at only $9-10. Do an internet search for it and you should find it. Good luck!
Robert, April 2016
