DIAGNOSIS This usually means the evaporator coil is frozen solid. The unit cools the coil to condense moisture, but if it gets too cold in the room or the air filter is blocked, ice builds up and it can't collect water.
FIX 1) Turn the unit off and unplug it. 2) Move it to a warmer room if possible (above 65°F). 3) Let it sit, doors open, for 8-12 hours to completely thaw. You can put towels underneath it. 4) While it's thawing, pull out the washable air filter (behind the front grille) and rinse it clean under warm water. Let it dry completely. 5) Plug it back in, make sure the bucket is seated perfectly, and restart it on a lower fan speed in the warmer room.
IF THAT DIDN'T WORK If it still doesn't collect water after a full thaw in a warm room, the refrigerant system might have a leak. Listen closely for the compressor to click on—you should feel warm air coming from the top grille and hear a distinct hum. If it's silent and blows cool air, that's a sign of a sealed system issue.
HEADS UP Running it in a cool basement (below 65°F) will cause this frost-up regularly. These are not designed as 'low temperature' dehumidifiers. Keep the filter clean and don't set the humidity level too low when it's chilly.