Chosen Solution
Just replaced my iPhone 6 battery and new battery working great. Problem is: there’s a small vertical strip down the middle of my screen that no longer functions. Makes it annoying to type and impossible to drag things from one side of the screen to the other. Any idea what the cause is, or how to fix? Thank you!
It simply sounds like your digitized connector isn’t plugged in all the way. I would suggest taking apart your phone again and removing the connector for the display to check for any damaged pins. if you see none put the connector back and ensure that it is plugged in all the way. If you still have issues, inspect the board closely for any components that you may have broken off or are missing. If all that checks out and you still have the issue, you could have touch disease, which is very unlikely but still possible.
