Diagnosis
The unit is getting power to the brain (control board) but the board isn't sending the "go" signal to the major components. This often points to a failed sensor, like the main humidity/temperature sensor, telling the board conditions are already met.
How to Fix It
Try a hard reset first. Unplug the unit from the wall for 5 full minutes. Plug it back in. Immediately press and hold the "ON/OFF" button on the control panel for 10 seconds. This reboots the control logic. Set it to a low humidity setting (like 30%) and see if it kicks on.
If That Didn't Work
The ambient temperature might be out of range. The Classic CW has an operating range, typically ~50°F to 90°F. If your crawl space is colder than the lower limit, it will lock out the compressor to prevent damage. Check the crawl space temp with a separate thermometer.
Heads Up
If it's not a temp issue, the main control board could be faulty. Before replacing it, check all the wire harness connections to the board are snug—vibration in a crawl space can loosen them.