Chosen Solution
Hello! You will most likely need a new screen. But, to first check if the cables are loose or not, follow this guide up until the steps to remove the screen cables. Remove them, the reattach them. Reconnect the battery, and turn on the phone. See if that fixes the problem. If not, you will have to replace the screen. Disconnect the battery and follow the rest of the guide to replace the screen. It should work fully again! iPhone 6 LCD and Digitizer Replacement
