Get a new rubber (i like the long ones). Poke it in the carb first. 5mm allen key helps, it wont want to go, it needs to be lined up perfect. Push the centre pin in the rubber. Slide the boot up, put the cross pin in.
Spark plug out of the motor and test for spark and no spark. Good to go.
It is easier to do this with the carb off the manifold.
Rarely do they not work as they are meant too.
A new rubber usuaully fixes them. If its anything else its usually me having to undo the bodge that someone has done trying to fix this issue the impropper way.
Bob.
