There have been multiple reports of dead MODE LEDs in Bus Pirate v3, preorder 2. The cause seems to be a dirty contact on the LED. Most can be repaired by reheating the joint, and possibly adding a bit more solder.
In response to this problem, Seeed Studio has changed LED suppliers. We also implemented a visual LED inspection step to the self-test in firmware v3.6 and later. If you have a dead LED and would like replacement parts, please contact us.
A note from Seeed follows.
Since some of previous MODE LED are reversed, we isolated manufacturing causes but regard the LEDs as defect supply. Either because of its soldering pad getting dirty or reliability issue. All future LEDs we are using are switched to a different supplier. If people demand replacement or spare parts, please help collect a list and we will send along. Sorry for the trouble brought!