Karcher SC1122 steam cleaner starts to heat up then stops? any idean?

When I turn on the steam cleaner the amber light comes on and the water starts to heat up, then after a few minutes it just stops. I have emptied out all water, refilled and started again even with warm water, still it does not heat up enough for steam to be made. Can you suggest something to fix this please? Has anyone else had this problem? Is this a repairable fault or do I just look for a new one? Thank you.