The answer to 'GFCI outlet outlet not working' is that there are several common causes, including a tripped GFCI, a wiring issue, or a faulty GFCI device. GFCI outlets are designed to trip when they detect a ground fault, which can happen due to water exposure, a short circuit, or other electrical issues. If the GFCI is tripped, you can try resetting it by pressing the 'reset' button. If that doesn't work, there may be a wiring problem or the GFCI itself may need to be replaced.
In some cases, the GFCI outlet may be working properly, but other outlets downstream on the same circuit are not. This could indicate a wiring issue that needs to be addressed by a professional electrician. If the GFCI outlet still doesn't work after resetting, it's best to call in an expert to diagnose and fix the problem.