Dehumidifier Does not work and reports incorrect humidity
If the dehumidifier is working and producing water, I would look for other sources of water or moisture entering the space. To gauge how well the dehumidifier is working, calculate how much humidity (water) the unit removes in a given period of time and compare this figure to the specifications or capacity of the unit. Your comparisons won't be exact but you can be close. If the dehumidifier seems to be performing as it should, look elsewhere for a source of excess humidity. As far as the reading on the dehumidifier itself, I would not rely too much on it being accurate. I would buy another gauge and compare the 2 numbers. If you really need an accurate figure there are devices called sling psychrometers you can buy that will give you an exact reading reading. To consider sizing of a dehumidifier, I have 4000 sq. ft. of finished and conditioned space, and have a 70 pint rated dehumidifier that runs about 18 hours a day to keep the humidity below 45%.