i guess you need to determine where the fault is:
*the actual light: very unlikely cos it's LED, and these generally last forever
*wiring within the hatch: possible, unlucky/unlikely; connection may have worked loose
*wiring that passes through the rubber tube between the main body and the hatch: could quite possible have a wire breakage here due to repeated movement/flex
*wiring in the main body of the car: could be, unlucky/unlikely
*fuse: not sure which fuse it's connected to, but worth checking
if there's a major wiring fault, some of the other electrics may be faulty too. so, questions for you:
1. does the boot light turn on when you open the hatch? the switch is within the lock, so it relies on a trigger here, so a major wiring fault could also take out the light
2. does the boot 'release' when you press the boot-release button (in dash or key)?
lastly, is the car still under warranty?