If you can tune a Kimber Montana, a FWB 124 is a piece of cake. Recently acquired and rebuilt a clean FWB 300S Match. My faithful FWB 124 is next. Parts came from ARH.
The 124's are pretty bombproof but if abused, the top of the cylinder/piston can be worn beyond repair and dry firing will break springs and score cylinders. Your rifle's failure to launch a pellet is not a good sign. Use a 3/4" pipe clamp with adequate travel and a piece of wood dowel fit to the aft end to clear the safety. Spill its guts and see what's what to set your next move. Or just cut a check to a reputable tuner to do the same....
