First, try cleaning the screen thoroughly with a microfiber cloth. If there is any residue, a little bit of rubbing alcohol or screen cleaner should remove it.
If you have a newer capacitive touchscreen, the stylus may be turning off to save battery. Try touching the back end of the stylus to turn it back on, or try using your finger on the screen to see if it responds.
If this does not help, you can try a touchscreen calibration. Go to Main Menu>Utilities>Configuration>Preferences>Touch calibration. Follow the steps. If the touch calibration does not solve the problem, the screen may need to be repaired. Please contact us through the support page.
If your tablet is an i400, there are no longer replacement screens for that model. If it does need the repair, options are:
Option #1: Operate the tablet with a mouse
Option #2: Upgrade to i535 tablet and dock for $1,700 with return of old tablet
Option#3: Downgrade to a 9.7” tablet plus dock for $600 with return of old tablet