I had an issue where the Gnome extension ‘Touchpad Indicator’ stopped working on my xps 13 (Arch). After looking a bit further, it seems that the Gnome Touchpad settings had also stopped working. All I could see was the mouse settings, and the touchpad section was completelly gone.
Solution:
With Gnome 3.20, xf86-input-synaptics is not longer supported, and you should use xf86-input-libinput instead.
You can check what is installed on your Arch system with pacman -Q | grep input. In my case, I had both packages installed:
$ pacman -Q | grep input
inputproto 2.3.2-1
libinput 1.8.2-1
xf86-input-libinput 0.26.0-1
xf86-input-synaptics 1.9.0-1
xorg-xinput 1.6.2-1
Remove xf86-input-synaptics and any configuration file (like /etc/X11/xorg.conf.d/50-synaptics.conf), install xf86-input-libinput and reboot. That should get your configuration working again.
