The answer to 'my smoke detector won't turn on' is that there are several common causes, including a dead battery, a faulty detector, or an issue with the electrical wiring. Smoke detectors typically run on battery power or are hardwired into your home's electrical system. If the detector isn't receiving power, it won't be able to turn on and function properly.
Some common symptoms of a smoke detector not turning on include no LED indicator light, no audible test alarm when the test button is pressed, and the detector not responding when you wave smoke near it. To troubleshoot, first check the battery and replace it if needed. If that doesn't work, the detector itself may be faulty and need to be replaced.