The answer to 'why is my dehumidifier' is that there could be several common causes, including a malfunctioning compressor, clogged air filters, or a problem with the drainage system. Symptoms may include the dehumidifier not turning on, not removing moisture effectively, or leaking water.
If your dehumidifier is not working properly, you'll want to first check the air filters and clean or replace them if they are dirty. You can also try resetting the unit by unplugging it for a few minutes. However, if the problem persists or you suspect a more serious issue like a compressor failure, it's best to call a professional HVAC technician to diagnose and repair the issue.