did you find the right button?
1. ensure you have power to the van. Check n the microvave or AC if you have them. They only work on 240V
2.There is a little on/off rocker switch 'hidden' in the hot water system. You access it on the outside of the van by removing the hot water system cover and with a bit of searching yu should see it there. Switch it to 'on'
3. Run the hot water tap to make sure there is water in the system.
4. wait 20 minutes and you should be OK