Make this small change if tapping on touchpad is not working

Ctrl + Alt + F1
Type below commands
1. nano /usr/share/X11/xorg.conf.d/40-libinput.conf
2. In the section for touchpad add below line just before EndSection
Option “Tapping” “on”
3. Press CTRL+X, then press Y, and press Enter to save the file.
4. Reboot the system