Several things to Check
Firstly is the power supply correctly plugged in to the booster, it is usualy a black cable which plugs into the under side of the booster.
Next is more dificult to check,is there powere in the 12v cable. On our last van the cable had an intermitent fault solution was to get a new cable.
Have you checked the other 12v appliances in the van.
This may sound stupid but is the booster switched on as there are 2 buttons underneath, 1 is on/off the outher is to boost the signal, wouldnt be the 1st time I switched the wrong one.
