4WD Still Not Working

[The Lang-Shankit Scunner]

All is working when press the button, relays click, centre actuator for front prop engages, add relay clicks, 4L makes all the same clicks and activates centre actuator. Vacuum works properly, and have replace all vac lines as precaution. Still no 4WD light on dash and no 4wd either. Switches on add and connectors on add all cleaned and electrical contact spray applied. Pulling hair out now. Oh and fuses are perfect also.

Help anyone?