If your strip lights do not light up, what should you do? 
*Wire color does not always matter! Make sure you follow the positive side of the flex strip down through the solderless connector wire to the power supply. Red/black can either mean (+) or (-) depending on what side of the LED flex strip you have hooked the connector too.
*Another common problem is that the solderless connector may be installed upside down; repeat steps above and try again.
*Also, MAKE SURE the tray is closed all the way. Be gentle!
*Check your power supply and make sure it is hooked up properly, with correct (+) and (–) as well.
*Are you using 12v LED strips with a 24v Power supply? This will not work. Make sure the power unit.
*How many feet of the LED strip are you using vs how large your power unit is? If you are using 1 reel of 24v Ultra bright with e 2.5amp power unit, it will not work because the power unit is too small.