Due to nature of physical and logical properties of this type of sensor it is important that your body (You) have some kind of ground connection - this will amplify sensor reading values and your touch will be register when you meet specific threshold.
Easiest way to ground yourself relatively to vehicle is to touch some metal part of it - like brake handle, stem, steering tube or even just holding the grips will do the job. Since version v6 touch sensor is more sensitive. Since version v5 touch sensor will not work while accelerating with thumb throttle pressed down.
If you encounter further problems:
please check soldering points on provided metal plate
reconnect module from Julet connector (plug/unplug) - it will recalibrate sensor - do the recalibration process after soldering metal plate
check continuity of pink (or violet/purple) cables, especially near resistor on this cable
contact us.