Touch screen not working

Generally there aren't too many explanations for why the touch screen fails when some other repair is being done. The digitizer cable may have been torn, the connector damaged, or simply just not plugged in completely.

Outside of the front sensor connector at the top of the screen, the other two connectors are for the OLED display and the digitizer. If the touch screen isn't working then you'll need to focus on this connector.

First thing to do is to open it back up and check the connector on both sides, the motherboard and the flex cable. Use a magnifying glass and a bright light and check for missing or broken pins. Check the logic board around the connector for any missing components; sometimes they can get knocked off in the process of trying to plug those connectors in.

If you find any issues with the pins, bent ones can sometimes be straightened with some fine tip tweezers, while missing ones are more problematic. If the flex cable connector is damaged you can simply replace the screen, but if something's wrong with the motherboard connector you'll need someone experienced in microsoldering with a hot air station to fix it.

Assuming you haven't found anything wrong with the connectors, go over the flex cable with a fine tooth comb looking for any kind of damage like tears or excessive bends that have cracked the circuit traces. Again, the fix for that would be a new screen.

Once you get to this point, clean both sides with 90% or higher concentration isopropyl (rubbing) alcohol. Reassemble the screen, paying special attention to the note regarding plugging in those FPC connectors.

To re-attach press connectors like this one, carefully align and press down on one side until it clicks into place, then repeat on the other side. Do not press down on the middle. If the connector is misaligned, the pins can bend, causing permanent damage.

There are a couple of notes to pay attention to specifically regarding the digitizer connector that bear keeping in mind as well.

This connector's recessed location makes it tricky to reconnect. Take your time and align it carefully, then gently press it into place with your fingertip—first one side, then the other. You should feel it click into place.

If any part of your screen doesn't respond to touch after your repair, disconnect the battery and then re-seat this connector, making sure it clicks fully into place and that there's no dust or other obstruction in the socket.

If it still doesn't work, then about the only other thing you can do is to go ahead and replace the screen in hopes the problem is on the screen itself and not on the motherboard.

Hopefully something in here will help. Give these suggestions a try then come back and let us know what you found and we'll see if we can figure out what the next step should be if needed.

Oh, and just to address your comment, if the digitizer is damaged, then the only solution is to replace the screen. It requires specialized equipment and expertise to successfully separate the OLED and the front glass digitizer, then more equipment to bond a new digitizer to the OLED. It's not even close to being cost effective to try and do that yourself, and the chance of success isn't all that good anyway.