Ubuntu – Touchpad tap stopped working

IT IS SCARY YET EASY TO DO, DON'T BE SCARED MY CHILD

try this if neither of the previous ideas of this thread worked:
In a terminal enter :
xinput
you should get something looking like this :

⎡ Virtual core pointer                      id=2    [master pointer  (3)]
⎜   ↳ Virtual core XTEST pointer                id=4    [slave  pointer  (2)]
⎜   ↳ ETPS/2 Elantech Touchpad                  id=14   [slave  pointer  (2)]
⎜   ↳ MOSART Semi. 2.4G Wireless Mouse          id=10   [slave  pointer  (2)]
⎣ Virtual core keyboard                     id=3    [master keyboard (2)]
    ↳ Virtual core XTEST keyboard               id=5    [slave  keyboard (3)]
    ↳ Power Button                              id=6    [slave  keyboard (3)]
    ↳ Video Bus                                 id=7    [slave  keyboard (3)]
    ↳ Video Bus                                 id=8    [slave  keyboard (3)]
    ↳ Sleep Button                              id=9    [slave  keyboard (3)]
    ↳ USB Camera                                id=11   [slave  keyboard (3)]
    ↳ Asus WMI hotkeys                          id=12   [slave  keyboard (3)]
    ↳ AT Translated Set 2 keyboard              id=13   [slave  keyboard (3)]

Even though it is scary, it is actually very easy to understand; now locate your touchpad, mine here is called is called "ETPS/2 Elantech Touchpad" (on the third line).
now, once you've done this enter :
xinput --list-props "whatever your touchpad is called"
for instance mine would be
nathan@linux-engine:~$ xinput --list-props "ETPS/2 Elantech Touchpad"

Once you've done this, Lotta lines should appear, for me it is :

Device 'ETPS/2 Elantech Touchpad':
    Device Enabled (135):   1
    Coordinate Transformation Matrix (137): 1.000000, 0.000000, 0.000000, 0.000000, 1.000000, 0.000000, 0.000000, 0.000000, 1.000000
    Device Accel Profile (263): 1
    Device Accel Constant Deceleration (264):   2.500000
    Device Accel Adaptive Deceleration (265):   1.000000
    Device Accel Velocity Scaling (266):    12.500000
    Synaptics Edges (288):  123, 2974, 114, 2005
    Synaptics Finger (289): 1, 1, 0
    Synaptics Tap Time (290):   180
    Synaptics Tap Move (291):   165
    Synaptics Tap Durations (292):  180, 180, 100
    Synaptics ClickPad (293):   1
    Synaptics Middle Button Timeout (294):  0
    Synaptics Two-Finger Pressure (295):    282
    Synaptics Two-Finger Width (296):   7
    Synaptics Scrolling Distance (297): 75, 75
    Synaptics Edge Scrolling (298): 0, 0, 0
    Synaptics Two-Finger Scrolling (299):   1, 1
    Synaptics Move Speed (300): 1.000000, 1.750000, 0.053305, 0.000000
    Synaptics Off (301):    0
    Synaptics Locked Drags (302):   0
    Synaptics Locked Drags Timeout (303):   5000
    Synaptics Tap Action (304): 2, 3, 0, 0, 1, 3, 0
    Synaptics Click Action (305):   1, 3, 0
    Synaptics Circular Scrolling (306): 0
    Synaptics Circular Scrolling Distance (307):    0.100000
    Synaptics Circular Scrolling Trigger (308): 0
    Synaptics Circular Pad (309):   0
    Synaptics Palm Detection (310): 0
    Synaptics Palm Dimensions (311):    10, 200
    Synaptics Coasting Speed (312): 20.000000, 50.000000
    Synaptics Pressure Motion (313):    30, 160
    Synaptics Pressure Motion Factor (314): 1.000000, 1.000000
    Synaptics Resolution Detect (315):  1
    Synaptics Grab Event Device (316):  1
    Synaptics Gestures (317):   1
    Synaptics Capabilities (318):   1, 0, 0, 1, 1, 1, 1
    Synaptics Pad Resolution (319): 32, 31
    Synaptics Area (320):   0, 0, 0, 0
    Synaptics Soft Button Areas (321):  1548, 0, 1737, 0, 0, 0, 0, 0
    Synaptics Noise Cancellation (322): 18, 18
    Device Product ID (255):    2, 14
    Device Node (256):  "/dev/input/event5"

But it is alwright! If you look carefully you should be able to find the a line saying "two fingers scrolling". for instance, mine is at Synaptics Two finger scrolling (299). If the values in that line are something else than 1, 1 then BINGO here are the problem ! just type :
xinput --set-prop "touchpad name" "scrolling option" 1 1
mine is
nathan@linux-engine:~$ xinput --set-prop "ETPS/2 Elantech Touchpad" "Synaptics Two-Finger Scrolling" 1 1.
it should be working now :)

You'll have to this everytime you restart your computer though !
Now it is time to automatized that everytime you wake up your computer :
In your home folder (or wherever you want) make a file named as you wish. it should contain

#! bash
xinput (the command) ...

Then in the search for an application name startup applications and press "ADD". Name it as you wish and write in the command Field bash /your/file/path. example. It is done, forever :D !!!

This instructions solved the issue for me on a Lenovo G50 + Mint Cinnamon 17

http://www.evilcodingmonkey.com/2014/01/23/ubuntu-activate-multi-touch-on-elantech/

Copy-paste (code typo fixed and a bit more of info added), as backup

First, if you aren't sure your computer was built with an Elantech touchpad, open a terminal, and type the following:

cat /proc/bus/input/devices

You should find a block containing a line looking like this one, which confirms you are on an Elantech touchpad:

N: Name="ETPS/2 Elantech Touchpad"

or

N: Name="PS/2 Elantech Touchpad"

Download this archive (from Ubuntu's bug reporting page).

Open a terminal, and follow these steps (after step 4, you will have no mouse at all):

cd ~/Downloads 
sudo dkms ldtarball psmouse-elantech-x551c.tar.gz 
sudo dkms install -m psmouse -v elantech-x551c 
sudo rmmod psmouse 
sudo modprobe psmouse

Enjoy multitouch!