The answer to 'why is my dehumidifier not turning on' is that there could be several common causes, including a tripped circuit breaker, a faulty power cord or outlet, a malfunctioning humidistat, or an internal component failure. The dehumidifier may not be receiving power, the controls may not be functioning properly, or there could be an issue with the compressor or other internal parts.
First, check the power supply by ensuring the dehumidifier is plugged in securely and the circuit breaker has not been tripped. If the power is working, examine the control panel and humidistat to make sure they are set correctly. If those basics are in order, the problem may be with an internal component, which would require professional repair or replacement of the dehumidifier.