Proximiy sensor not working after disassembling

Hi ifixit-team!

I have a very strange problem with my Xperia X Compact. I got the phone from my cousin. It was used, but fully working, only the head phone jack was defective.

So I bought a new one, disassembled the phone and replaced the jack. I have some experience in repairing phones and think I know what I do.

As you might know, during the disassembling you have to disconnect the sensor bar (with the ambient light and proximity sensor) temporarily from the main board, its a ZIF plug.

After I reassembled my phone again, the proximity sensor was not working anymore. I double-checked the connection of the sensor bar to the main board, but everything seems just fine. The interesting part: the ambient light sensor and the proximity sensor are ONE electronic part. My ambient light sensor is working well, my proximity sensor is not working.

The proximity sensor does not recognize my skin at all. The ONLY thing it still recognizes (used sensor multitool to test the sensor) is white paper or metallic objects. And that only, if they are like 2-3 mm away from the phone.

I have read about exactly this problem under a YouTube video about disassembling the phone, and in one thread on XDA. The guys there also bought new sensor bars, but there ONLY the proximity sensor did not work, too. So I assume this has to do with the SOCKET on the main board, not the flex cable?

I want to emphazise that I did NEVER touch the sensor at all. I only shortly disconnected the flex cable of the whole sensor bar shortly from the main board, and afterwards the sensor was defective. You guys are my last hope, as I am a very poor student. It also seems that few people bought the Xperia X Compact, so there are not very many people on the internet talking about hardware problems or fixing the phone….

P.S.: Of course I also tried cleaning my phone or testing the sensor outside the phone AFTER it went defecitve. No change in behaviour.