Let's just say you wanted to fix that fixture. You can. Chances are all 24 LED's are wired in series ----LED1----LED2---LED3---. One of the LED's is bad, so the entire fixture is dark.
Take a pair of tweezers or a thin wire and one by one short out each LED (connecting the wire to both sides of the LED's contacts at the same time). When the fixture lights up, poof, you have your culprit. Simply solder a permanent jumper wire, and your fixture will keep going, probably for a while. The 23 remaining LED's will shoulder the load.
Take care as the white and black wires are high voltage from your light switch. The LED's themselves have only a harmless voltage. Search your favorite video site for tutorials on diagnosing LED premature death. Or, find a local kid interested in experimenting with this. Or check out a safer method at Instructables ( http://www.instructables.com/id/Repair-Dead-COB-LED-Light-Bulbs/ ).
The problem with cheap LED fixtures is they don't actually pay out: if you have to landfill them, the energy savings is not worth it. Consider buying a fixture with screw in bulbs, and then bulbs from a quality vendor such as Cree. Never get anything from a big box store: the energy efficiency is poor and the quality is suspect. Insist on at least 95 lumens of light output per watt of energy used.