Switch off the appliance and unplug it. Check if the filter is placed properly in the juice collector. The ribs in the bottom of the filter have to fit properly onto the driving shaft. Check if the filter is damaged. Cracks, crazes, a loose grating disc or any other irregularity may cause malfunction.
If you detect any cracks or damage in the filter, do not use the appliance anymore and contact the Philips Customer Care Centre in your country for replacement of the filter