Diagnosis
The compressor likely isn't kicking on. This can be a refrigerant issue, but more commonly it's a clogged or frozen evaporator coil preventing the cooling cycle.
How to Fix It
1) Turn the unit off and unplug it. 2) Open the front grille (it usually just snaps off). 3) Look at the cold coils behind the filter. If you see a solid block of ice, that's your problem. 4) Let it thaw completely—this can take many hours. A fan pointed at it can help. 5) Before restarting, check that your air filter is clean and that you're not running it in a very cold room (below 65°F). Low temps can cause it to freeze up again.
If That Didn't Work
If the coils were clear and it's in a warm enough room, the issue might be low refrigerant, which isn't a user-serviceable fix. You'd need to contact Friedrich support.
Heads Up
Running it continuously in a damp, cool basement is a classic way to cause coil freeze-up. Consider using the built-in humidistat to cycle it on and off, or get a separate timer to give it regular breaks.