The answer to 'my dehumidifier won't turn on' is that there could be several common causes, such as a tripped circuit breaker, a clogged air filter, or a faulty dehumidifier. First, check the circuit breaker and reset it if it has tripped. Next, inspect the air filter and clean or replace it if it's dirty. If those basic troubleshooting steps don't resolve the issue, the dehumidifier itself may have a mechanical or electrical problem that requires professional repair.
If you've checked the basics and the dehumidifier still won't turn on, it's best to call an HVAC technician to diagnose and repair the issue. Attempting to fix a dehumidifier yourself can be risky if you don't have the proper training and equipment, and could result in further damage or even safety hazards.