Lights Don't Come On
First, check all your connections and make sure they are tight. The screw terminal may be the culprit. Check to be sure your wires are stripped enough, and the terminal is clamping down on bare wire instead of on insulation. Tug on the wires to make sure they're in there really firmly.
On occasion you get a screw terminal that just won't hold the wires very well. Try replacing the DC jack if this seems to be the problem.
Next, check to be sure you've uploaded the code to your microcontroller. For the Flora: when an upload is successful you'll see a red light come on and slow-blink (that means you're in bootloader mode), then you'll see a yellow LED flash for a moment (that means the Flora is receiving code). If you don't see this light sequence on the Flora, your code didn't upload correctly. Try hitting the reset button and uploading again.
If it seems to be uploading correctly but the light strand still doesn't come on:
Be sure that your code and your actual physical pin connections match. The code expects you to have connected your lights to pin #6. If you've connected to a different pin, update the code to match.
Also make sure you've got the three connector wires going to the correct pins -- it's easy to get them mixed up.
Lastly, check again on the back of the pixels to make sure your Flora is attached at the "in" end of the strand and not the "out" end.
Code Won't Upload
Check to be sure that the correct board is selected from your Boards menu. Don't see it there? Head back to the Software page and follow the directions to get it installed.
Also check to be sure that under
Tools > Port .. you can see and select your microcontroller. Don't see it there? Try a different USB cable, or try plugging your USB cable directly into your computer if it's going through a hub. Still don't see it? Try rebooting your computer.
Be sure you've installed the FastLED library (
Sketch > Include Library > Library Manager..) You may need to update the library if you have an older version.
If you still can't get the code to upload, back up and try uploading sample sketches from the NeoPixel library Examples folder. Be sure you can get the StrandTest sketch to work, then try this sketch again.
Lights Come on but Misbehave
If only some of the lights come on, take a look at the code you uploaded and make sure you've changed this line:
#define NUM_LEDS 400 // Change this to reflect the number of LEDs you have
..to reflect the actual number of LEDs you have. It's OK to make this number too big, but it's a problem if it's too small.
If you get just one or two lights coming on in white or green: You may have your power and ground connections switched. Double check to make sure you soldered the connector on right.