The most common issue is the leaking compressor component for your case. Adding 氟 is not going to help and 氟 will be leaking anyway.
if it is in 5 year warranty for your compressor, you need to get diagnois reports from approved service company. It will cost about $50. If the compressor is not under warranty or if the defects are also from other components out of warranty, the repair itself will cost you $200. In this case, you had better buy a new dehumidifer.