Just want to varify that you tried F6 (without pressing the function key), that turns the touchpad on and off. If both that and a restart don't work, I think you'd need to have your computer looked at.
Was there any update or modification before the issue occurred?
What happened when you press F6, does it show touchpad on and off?
or only off.
Please help to find out if there is any error message in Device manager
and reinstall touchpad driver.
Thank you very much.
ASUS have updated ScreenPad to Screenpad 2 and in the process broken for most (for the UK at least) the ability to use the screen pad correctly. You can following the extensive instructions to upgrade BIOS and the Screen Pad but in turn you will loose much of the functionality as the new AppDeals app required to install additional apps is not available in some territoties, like UK. ASUS themselves when contact keep giving the same information which is pointless rather than listening to people who have spent a lot of cash on their new laptops.