Possible Causes

Blown incandescent bulb (older models), failed LED module, faulty door switch, loose light connector

How to Fix / Troubleshooting

Safety: Unplug the appliance before replacing bulbs or LED modules.

Steps:

Check bulb: On models with replaceable bulbs, remove the cover and inspect the bulb. Replace it with the correct type and wattage specified by Neff.
LED modules: For LED lighting, the entire module may need to be replaced. Remove the light cover and check the connector.
Door switch: Test the door switch or reed sensor; if it does not signal that the door is open/closed, replace it.
Connector: Ensure the light module connector is firmly seated.