Tell us about yourself!
LED Christmas Tree With Video Projector (Rasp Pi)
LED Christmas Tree With Video Projector (Rasp Pi)View Instructable »
I actually had the same issue initially until I realized that the ground of the LED strand needed to be tied to the ground of the Raspberry Pi. One I did that the entire strip lit up. Not sure if you are running into the same issue with your wiring, but thought I'd throw it out there.
Arduino Controlled Positional RGB LED Christmas Tree
3D printed CNC mill
Arduino LED Strip Crib/Bed Night Light