Gsync doesn't work as long as f.lux is running
This is just an FYI in case anyone else happens across this problem. The current version of f.lux (4.76) causes nVidia's Gsync to not activate as long is f.lux is running (even if it's set in "deactivated" mode). For those with Gsync monitors, this means no games or other full screen applications will be able to make use of it.
Hopefully future versions of f.lux will allow Gsync to function without having to completely shut if off.