Having enjoyed using Wacom products for many years, I have had a number of issues with the touch settings / functionality of the later Intuos models. Recently my touch settings stopped working entirely. I restarted my machine and the Wacom drivers, all to no avail. This morning I got to the bottom of the issue.

System Preferrences > Security & Privacy > Accessibility > Click Lock to Makes Changes

Scroll to the bottom of the a list of apps and make sure that WacomTouchDriver.app is checked. If it isn’t checked then check it. This will give Wacom the system level access it requires to use touch. If WacomTouchDriver.app is already checked, then uncheck the app and check it again. This worked in my case, the toggling of the radio button appears to re-boot the privacy settings.