I've had this exact problem in the past. Wasn't an easy fix for me unfortunately.
Turns out the wiring had all frayed on the switch (due to VW not leaving anywhere near enough slack and the way the boot opening handle bends). Had to get the whole thing rewired.
Id suggest trying to remove the plastic around it (that's also a pain in the arse to do as well but preserve and try your best not to scratch the plastic with the screwdrivers) and see if you can see the wiring the prove its the same problem.
Let us know how you get it on, its a right old pain not being able to open your boot.