One light doesn't work. Why,?

Hi,

Perhaps the bulb may be blown or is not screwed in tightly enough.

Here’s the ifixit Milton Bradley Simon Light Bulb Replacement guide that shows how to replace the bulbs.

Usually the bulb rating information is stamped on the metal collar part of the bulb either the voltage and power (Volts & Watts) rating or perhaps the voltage and current (Volts & Amps) rating.

The bulbs appear to be a miniature Edison screw type.

Try swapping two of the bulbs i.e. the suspected faulty one and a good one, and check if the problem moves to the other position or not. This is just to verify if the bulb is good or not or if the problem is with the light’s position. This is of course if you can’t tell if the filament in the bulb has burnt out ;-)