What would cause a Jake Brake to not work ?

Jake break Solenoid.

 

Clutch pedal little loose therefore depressing clutch switch maybe? Same for brake pedal but that's easier to see it should light up your brake lights

 

Definitely clutch switch or loose clutch pedal.while driving lift your pedal by placing your foot underneath it and try to set your cruise or engage the jake brake and you’ll know for sure

 

Years ago, there were 3 controls for the engine brake. The dash switch, the one on the clutch pedal, and one on the throttle. Not sure how its done today. I think what you did for less play only delays the inevitable, you need a clutch.

 

Usually you can hear a click sound when it either engages or disengages the switch when clutch pedal is either fully at the top or depressed a bit. If you really wanted to check you could hook the computer to it and see what ecm is seeing as far as clutch/brake/fuel pedal position sensors are telling the ecm. The switch itself could be bad. Also can look what the ecm is seeing as far as cruise on/off, if it detects when you push set, same for jake on/off. But considering they're both not working I'd be surprised if it's anything other than your pedal sensors.

 

IF the clutch is shot and you added something to the clutch linkage that isn't supposed to be there then you created another issue. Simplest thing is to get the clutch replaced and undo the "creative re-engineering" that you did