Hi,
Try installing the latest Asus [https://www.asus.com/us/Laptops/ASUS-ZenBook-UX31LA/HelpDesk_Download/|ATK package drivers] and check if that resolves the problem.
You may have to [https://bloatwareuninstaller.com/uninstall-guides/remove-asus-atk-package/|uninstall] the old drivers first if it won’t update.
If you have Win 10 installed, there are more up to date ATK drivers available from [https://ivanrf.com/en/latest-asus-drivers-for-windows-10/|here]. Read the ''Notes:'' near the top of the page in this link on how to install the drivers from this link. Just ensure that you get the correct ones for the Win 10 OS installed in your laptop, i.e. 32-bit or 64-bit. To find out which version you have, go to ''Windows Start button ( left side of Taskbar) > Settings > System > About'' and find ''Device Specifications > System Type''.