At some point during the most recent firmware update, or two, my Pebble no longer turns on the backlight when I flick my wrist. (Prior to the 1.9.0 update, I know it worked fine. I can't remember if it worked fine between that and the 1.9.1 update...)
I've read the FAQ's and tried tapping Pebble near the strap, but no luck.
I've reset Pebble to factory default multiple times, rebooted, shutdown and recharged.
I've modified the "Backlight Behavior" option with no luck either.
Pebble + Verizon Galaxy Nexus, Jelly Bean 4.2.2 via JDX with Lean Kernel