it's operated by a solenoid so either the motor is knackered (most likely) or the cable has come off (less likely) or broken (even less likely)

stand by the boot and listen when someone presses the release button if you can hear the motor going then it's working, if not you know what the issue is

i did this on my mk4 and cut my hands to shreds sticking them up in the panel so be sure it's what you think it is rather than just trying random stuff

it will go together, just make sure you take plenty of pics as you take it apart