I have experienced this happening 3 times now. The latest was this scenario.
While riding up a long, about 8% grade, I need to downshift. I click the paddle switch and there no shift. I keep tapping the paddle and still nothing. I stop and look at the LED on the shifter. it glows when I push the paddle. I bounce the bike up and down several times and then I can see the derailleurs LEDs turn on. I shift again and the rear derailleur shifts.
It appears that my system is going to sleep on long steeper climbs and wont turn on unless I have some sort of larger impact to the vibration sensor/s. I am starting to wonder if the vibration sensors are not sensitive enough, and/or do not work at steeper angles. (This is happening on gravel road climbs, not smooth asphalt, so there is a lot of bike bouncing and road impacts.) (I have about 800 miles on the this EDS TX.)