。
The bathroom light isn't working.
Literal
Bathroom [possessive-の] light [subject-が] turn-on-not.
電気 literally 'electricity,' but used colloquially to mean 'light / lamp' (the fixture, not just the power). つく (intransitive 'turn on / come on') contrasts with つける (transitive 'turn [something] on'). つきません is the polite negative. Common complaint phrase for malfunctioning appliances.