Auxiliary heater Webasto Air Top 3000 won’t fire up

[Dale Green]

Hi my heater goes through the startup procedure but isn’t getting any diesel fuel supply from the pump ( pump not clicking as it should ). VCDS shows no faults and neither does the heater control panel in the vehicle ( 2005 VW California Comfortline LHD ). However, if I use VCDS Output tests, as soon as I test the fuel/metering pump it starts clicking away +- so it is working. Any ideas ? control problem ?