Had the same issue... reboot using this method. Fixed it.
How To Hard Reset / Force Restart iPhone X:
Step 1: Press the Volume Up button and then release, followed quickly by pressing and releasing the Volume Down button.
Step 2: Now quickly press and hold the Side button until you see the device’s screen turn off, followed by Apple logo showing up on the device.
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Step 3: Once the Apple logo appears on screen, release the Side button to complete the force restart cycle.
Same issue as well and a reboot fixed it. Funny my 6 plus did the same thing, thought it was Touch gate. A reboot fixed that too.
Also I know people with iPads including myself that does the same thing. Unresponsive to touch.