Maybe an external USB device (e.g an USB mouse) automatically disabled the touchpad. Turn off the laptop, disconnect all external devices and then, turn it on again.
If the touchpad starts working, that means that one of the external devices prevented it from working properly; however, if your touchpad still doesn't work, then something else is the problem (check out the other solutions).
If you don’t receive the email in the next 2 minutes please check your junk folder, and add [email protected] to your safe sender list.