Do you mean the white light on the NOW Stick?
If so and the white light struggles to come on when the Stick is powered up then a couple of things to try.
1. If using the 5vdc 1 A USB port on your television, then try the supplied power adapter or vice versa.
2. Try a different USB standard to USB micro cable.
3. If you have a third party USB 1 A charger, try that with the Stick.
Should the white light be flashing then that points to either a wifi / internet connection issue or an HDMI issue.