The problem could be a simple one that often stops an air conditioner from cooling, the filter and coils are clogged with dirt:
1 Unplug the dehumidifier, then remove and empty the water-holding tank.
2 Remove the front and back grills. You'll have to either use a putty knife and pry between the top of the grill and the cabinet body to release the catches, or use a screwdriver to unscrew the fasteners.
3 Remove the mesh filter, if your machine has one. It may be attached to the front grill or set in a track in front of the evaporator coils.
4 Clean the filter with a mixture of warm, soapy water and bleach. The bleach will kill any mold or mildew, so it won't be blown around the room when the machine is running.
5 Clean the evaporator coils, using a vacuum with brush attachment. Remove any stubborn dirt with a scrub brush and a household spray cleaner, such as Formula 409. Scrub lightly so you don't bend the fins covering the coils.
6 Inspect the fins. If they are flattened or bent, buy a fin comb at your appliance store and use it to comb up or down on the fins to straighten them.
7 Clean the condenser coils, using the vacuum and brush attachment. Again, remove any stubborn dirt with the scrub brush and spray cleaner.
8 Inspect the fins covering these coils. If they are flattened or bent, use the fin comb to straighten them.
9 Unfasten the cabinet body so you can get access to the interior parts. Use a screwdriver to remove the screws along each side of the bottom of the cabinet. Also check the control panel and the plastic drain tray that directs water into the holding tank. If any screws are holding these parts to the cabinet, remove them.
10 Remove the cabinet body. Grab each side, pull out slightly and then lift the body off the unit.
11 Clean the fan blade and the other parts inside the cabinet, using the vacuum and crevice attachment.
12 Reassemble the dehumidifier, reinstall the water-holding tank and plug in the unit.

ALso, could check thi "troubleshooting guide" in this link.

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