Just quoting the solution from other forum:
I have found a solution to the hardware fault on my phone, my microphone was never working so clearly hardware fault. I had the same microphone issues and the LED lights below my screen wouldn't work. I found that when i twisted my phone I could get them and the microphone to work, so it seemed like a bad connection in the lower daughterboard, upon disassembly I found the fault was actually where the ribbon from that board connects to the mainboard. In the picture below marked by the red arrow, I found that applying pressure made the Led's and microphone work. My solution was to stick a small piece of 2mm thick adhesive foam onto the silver cover so it applies pressure from the back cover.
Phone is working perfectly now
I have found a solution to the hardware fault on my phone, my microphone was never working so clearly hardware fault. I had the same microphone issues and the LED lights below my screen wouldn't work. I found that when i twisted my phone I could get them and the microphone to work, so it seemed like a bad connection in the lower daughterboard, upon disassembly I found the fault was actually where the ribbon from that board connects to the mainboard. In the picture below marked by the red arrow, I found that applying pressure made the Led's and microphone work. My solution was to stick a small piece of 2mm thick adhesive foam onto the silver cover so it applies pressure from the back cover.
Phone is working perfectly now