What DID work for me: press down on the screen with both thumbs to ensure the screen to ensure the screen connector (circled in yellow below) is in firmly, and the capacitive touch grounding strip (circled in cyan below) is in good contact with the phone's ground plane.
...from this tutorial. This is what the phone looks like just underneath the screen and touch panel under the screen. Notice the connector I circled yellow in the image above, and the rectangular grounding strip I circled in cyan underneath it. That'sThe yellow-circled item is the connector for the screen and touch sensor to connect to the phone, and the cyan-circled one is the grounding pad for the capacitive touch sensor. ItThe connector has a plate/cover on top of it (shown here) which screws down to hold the connector in place, so it is unlikely to move or lose contact, but perhaps may. The cyan-circled grounding pad is likely very critical to the phone's touch sensor operation, since personal electronics experience making capacitive touch sensors work with Arduinos (ex: see the touch lamp video at the top of my website article here) teaches me that capacitive touch is very sensitive to grounding issues.
I thought maybe pressing on that connector and grounding pad would help (truth be told: I actually was just thinking about the connector, and had forgotten about the grounding pad until after I had done this). So, I pressed firmly but carefully down on the top of the screen near that connector, and then near that grounding pad. I then repeated this process, pressing with both thumbs, moving down the screen lower and lower from on top of that connector and down, until I reached about 1 inch from the bottom of the phone. I couldn't remember where the connector was exactly at the time, so I pressed in these several places, with both thumbs at once. Then, I tried the phone again. Voilà! Magically it worked! Touch sensor seems fine now. It must have just re-seated that connector better is all, or: even more likely: regrounded the metallic strip from the capacitive touch sensor to that grounding pad circled in cyan/bluish. I hypothesize that the adhesive-attached grounding strip connected to that pad had come loose, so that the instant I touched my charge cable to the phone to charge it, the electrical potential of the phone's ground got altered (charged or discharged) by the charge cable's ground, causing the capacitive touch to quit working. Re-grounding the capacitive touch grounding cable to that ground pad underneath the screen must have fixed the capacitive touch sensing system (I think)!
