This just happened to my 15-month-old sense today. Just before a run. It wouldn't start an exercise (just hopped back to the home screen). The "Shut Down" option in settings did nothing every time I tried to select it (just went right back to settings after clicking it). So, I force rebooted it by holding the "fake" button for 10 seconds (RANT: The "fake" button was the worst "innovation" with this watch). It went into a boot loop after that.
I tried these button timing instructions (after doing my run with my 3 year old Garmin instead), but it just kept happily rebooting.
However, what I noticed is the boot loop isn't random. It boots after exactly 10 seconds every time. I don't think it's a coincidence that 10 seconds is the same amount of time you need to hold the "fake" button to force a reboot. Perhaps it was just "stuck down".
I briefly rinsed the watch with regular tap water (yay water resistance) thinking maybe it was sweat or oil from my skin or something causing the capacitive button to be stuck.
That didn't work. So, I dried it and left it to sit for a couple of hours while I worked. Then tried pressing the button a couple of times (not trying any timing thing or anything). Lo and behold it rebooted to a fat red X and a message saying "Data not cleared Sync & try again".
It wouldn't resync so I was stuck resetting it by following these instructions: https://community.fitbit.com/t5/Other-Versa-Smartwatches/Data-Not-Cleared-Synce-and-Try-Again/m-p/27...
It installed a firmware update after setting it up. So, I'm guessing that it needed a firmware update all along but never told me/applied it.
Annoying that I had to completely set up the watch again. But, at least it's not a paperweight anymore.
Perhaps the "Shut Down" option will work for me again when this update completes. 😛
Anyway, wanted to post this in case anyone is annoyed trying the button timing voodoo. I feel like the issue might just be a "stuck" button that you have to figure out how to get unstuck (pressing a bunch? Or cleaning?).
