The answer to 'why is my dehumidifier not heating' is that the heating element in the dehumidifier may be malfunctioning or broken. Dehumidifiers use a heating element to warm the air and remove moisture, so if this component is not working properly, the dehumidifier will not be able to heat the air.
Some common causes of a dehumidifier not heating include a faulty thermostat, a clogged air filter, or a problem with the compressor. If the dehumidifier is not producing any warm air, it's likely an issue with the heating element itself and will need to be replaced.