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Sorry to hear that you are having issues with your Surface 4. Before we start with any major troubleshooting steps, there are a few basics that i would like you to try. Also, please advise if this is a Surface 4 Pro or Surface Book.
Use a soft, lint-free cloth dampened with water or eyeglass cleaner but don’t apply liquids directly to the screen. To learn more, see Clean and care for your Surface.
Sometimes, all you need to get your touchscreen working again is a restart:
Step 1: Press the Windows logo key Windows button. (If you're using a mouse, select Start Windows button.)Step 2: Press the Tab key to select Power, and then press Enter. (With a mouse, select Power.)Step 3: Use the arrow keys to highlight Restart, and then press Enter. (With a mouse, select Restart.)