Cannot launch Karabiner Elements
I tried different iterations of these steps, but the one that ultimately ended up working was:


Uninstall the app via command line (since GUI wasn't launching):

sudo '/Library/Application Support/org.pqrs/Karabiner-Elements/uninstall_core.sh'

Reinstall the app via the installer. Do not launch Karabiner Elements.
Restart the computer.
While it's restarting, hold down command+option+p+r to reset the PRam. Let go after the Apple logo appears the second time.
Launch Karabiner Elements.