Dehumidifiers do not work well when the air temperature is lower than 40 degrees F. They rely on having a surface that is colder than the air to attract humidity. If the air temperature is below 40F the unit cannot get cold enough to attract moisture at the same rate that it does when the air temperature is warmer.
When the ambient temperature is above 95F or below 41F, the unit will shut off. This protects the compressor. to restart the dehumidifier, wait three minutes and turn the unit back on.