QuickJoy JetFighter sv 126 problem

[ElPolloDiabl]

It was common for the wires to rip on these things.
Find someone who is good at soldering (perhaps another Amiga user?)
and have them unscrew it and check the wires haven't come loose.

[ElPolloDiabl]

The wires inside the joystick. It is probably quite delicate inside. Only open it if you have done it before.
There are wires that go from the fire button to the bottom of the joystick. They connect to a circuit board before going to the cable. (Where the cable comes out of the joystick).
One those wires has probably broken loose.