If no compressed air is coming from a compressor, what could be the cause?

A sticky outlet valve can indeed prevent compressed air from flowing properly from the compressor. When the outlet valve is stuck, it won't open or close as needed, obstructing airflow and leading to a lack of compressed air output. A functioning outlet valve is vital for the efficient operation of a compressor, as it controls the release of air into the system.

In considering other possibilities, while a broken electrical connection can lead to the compressor not running at all, it is not specifically tied to the scenario of no compressed air being produced when the compressor is operational. Similarly, low tank pressure could certainly indicate that the compressor isn't able to fill, but it may not be the immediate cause of no air flow at the outlet. Lastly, a faulty gauge may misrepresent pressure readings but does not directly affect the physical ability of the compressor to produce and release air.