try taking the phone completely apart, and checking all the connections and letting it fully dry out if it isn't.
make sure the touch screen is receiving power from the charging port. Let us know if this helps or if you find something, good luck!
You have to do an advanced hardware reset by first removing the battery for 30 minutes. Set a timer. After 30 mins, replace the battery and hold the volume down button for another 15 minutes. Set a timer. After 15 minutes, release the volume down and press volume up button rapidly 3 times and then immediately remove the battery again, this time, also remove the sim card. Wait about 30 seconds, and replace battery and sim.
When you power the phone back on, you should get a prompt asking you which hardware component to update., Select "screen sensor" by scrolling through the options with volume down and select it by pressing volume up. The phone will now reset the "screen sensor" hardware data and download the newest hardware update for your phone.
Screen should now be fully functional.