I'm using gesture mode and I can't get the Spark to take a selfie. Is there something I need to turn on in settings?

Yes, if you're flying with phone or RC ensure that "Gesture Mode" in enabled

Hold the gesture for 3 Sec.. check this tut :

As Tviscomi said if using RC or phone make sure gesture mode is turned on in app, if using palm control within 7 meter use the sigh with two hands check slow flashing red front leds , ready now to take selfie.

I can usually get most of the gestures to work after a couple tries, but I haven't had any luck with the selfie one either.  You probably have to do it slowly and precisely at just the right distance.

I'm using without the iPhone or RC - I use all the gestures and they work fine. I wave it flyies away - I make a frame with my hands - the red lights flash 3x and then green but - no luck

all the gestures work. I even changed the micro SD Card - no photo!

Same for me... LED flash red quickly, then green. Guess this needs to be done at the right distance and slowly...?