Yoga C930 laptop. Suddenly today the touch screen has stopped working although the driver says it is working properly and is updated. ARRRGGGHHH. Suggestions?

Welcome to the Community Forums In2Caps,

Apologies for the late reply.

These are basic troubleshooting steps for your machine. 

Perform a static discharge/power cycle
- Make sure there is still remaining battery power, able to power up the machine.
- Disconnect all cables and/or peripheral devices connected to the machine (ex. power cable, hdmi cable, external mouse/keyboard, flashdrives, etc).
- Ensure that device is powered/switched off.
- Press and hold down the power button for as long as 60 seconds to drain flea power or excess voltage.
- The machine should remain in off state. 

Perform/load BIOS defaults
- Make sure that the machine is properly powered down/switched off.
- Find the Novo Button. How a Novo button should look like: https://support.lenovo.com/us/fr/solutions/ht062552 
- Access/click this by using an unfolded paperclip or by using something similar to the latter.
- Machine will power up to Novo Menu. Navigate and select using the arrow keys to BIOS Set Up.
- Inside the BIOS Set Up, navigate to the Exit Menu. Select Load Setup Default - click Enter, select YES and click Enter.
- Select Exit and Save Changes then click Enter, select YES and click Enter.
- The computer will start up.

Continue with the steps below.

1. Go to the Device Manager.
2. In the Device Manager, click View from the menu and click Show hidden devices option.
3. Look for Human Interface Devices in the list and expand it. Right-click and Uninstall everything that starts with HID and USB.  Or just simply uninstall the hid-compliant touchscreen driver only, then restart the machine.
4.  Restart the computer after uninstalling and check for touch functionality.
5. Proceed if the steps below did not work.
6. Boot to OKR: While the system is OFF press the NOVO Button and let it reach the OneKey Rescue interface where you have the mouse cursor available. Try using the touchscreen in the OneKey Rescue interface to see whether the touch function is responding. You can tell that it is working when a ripple is showing when you touch the screen. 
7. Boot to Windows Advanced Options: Hold the Shift Key on the keyboard then click Restart. This should bring you into the Boot Options Menu. Choose the Troubleshoot Option by touching the screen to select it. Check if it will respond with the touchscreen.

Update us how it goes.

Regard.

Dex_Lenovo