Chosen Solution
Hi Ernest, As the others have said this could be a quality issue, however I have had similar issues with the iPhone 6+ which was easily rectified. The iPhone 6+ has two rather long connectors from the LCD and Digitizer Assembly, one for each respectively. Due to their length, these connectors sometimes have issues making full contact with the headers. As they are slightly malleable, you will find they often flex in a concave fashion, or perhaps one end will be lifted. Removing and straightening the connectors so that they make full contact with the header is a quick fix, and can sometimes get you out of trouble if a new screen isn’t displaying or the digitizer isn’t functioning correctly. Again, this may not be the issue, but as the iPhone 6+ has longer connectors for the screen assembly, it is worth checking out. Calvin
I’m sure this has to do with the screen quality. You could disconnect the new screen and reconnect the old screen and see if the touchscreen works on that old screen, if it works it’s going to be a screen issue. Also try doing a soft reset holding down home button then power button until the apple icon comes on.
As Calvin said, The connectors are comparatively longer than 6 or 5 series, Many of the times the 3rd party replacements don’t align good and you don’t hear the click sound on snap in. Straighten the connectors again and try to feel the positioning with your finger don’t push it hard you will know by the feel when it’s ready to go in and snap it in if you don’t hear an audible click check again but if you hear a low click you are good. Press the connector with some force now and you should be good. Sal