Chosen Solution
So, I was given an iPhone 7 to repair which presented no sound or mic during calls. Tested speaker phone and voice memo. Mic was working, as was the speaker. Diagnosed a faulty earpiece speaker. Replaced the earpiece. Re-attached the LCD and camera flexes. Put battery + LCD shield back on, same with camera shield. Closed up and secured bottim screws. 4 minute job. All screws in correct place. Didn’t touch home button. Booted phone. Tested calls. All work fine, issue resolved. But… TOUCH ID not working, and unresponsive Home button. WTF??!! Any ideas?
“The iPhone 7/8 series have a very inconvenient bend on the Home Button flex. It’s really easy to tear the flex, either near the logic board connector or at the 90 degree bend before it sneaks underneath the LCD heat shield. You have to be careful when you lift the screen off the first time but also anytime the flexes are connected and you have the device open. You will need to carefully inspect the flex to see if there is any damage. Magnification here will help. Look for tears to the flex or any physical signs of damage. You should also check the connector to insure none of the pins are damage or that there isn’t any debris.” This is a cloned answer and all credits should go to @refectio , just to be clear, but I believe it may apply to your issue.
If you never removed the home button it may just need to be connected to Itunes. Not sure why but sometimes it needs to connect with itunes to clear the error.
