Make sure that you have pressed the on/off button on your VisaBoost properly.
Charge your VisaBoost according to the instructions in the user manual. Verify whether there is a power failure and if the wall socket is live. Check if the charging light on your VisaBoost lights up to make sure the appliance is charging. If it does not light up or if your VisaBoost still does not work, take it to your Philips dealer or the nearest Philips Service Centre.