Two finger scroll greyed out in Settings

edit

Rollback all change in ¨Mouse and Touchpad¨ and then:

Copy the /usr/share/X11/xorg.conf.d/50-synaptics.conf file to /etc/X11/xorg.conf.d/

cp /usr/share/X11/xorg.conf.d/50-synaptics.conf /etc/X11/xorg.conf.d/50-synaptics.conf

Then, in your favourite text editor, modify this file as such:

Section  "InputClass"
Identifier  "touchpad catchall"
Driver  "synaptics"
MatchIsTouchpad  "on"

####################################
## The lines that you need to add ##
# Enable left mouse button by tapping
Option  "TapButton1"  "1"
# Enable vertical scrolling
Option  "VertEdgeScroll"  "1"
# Enable right mouse button by tapping lower right corner
Option "RBCornerButton" "3"
####################################

MatchDevicePath  "/dev/input/event*"
EndSection

Have a nice time.