Can't detect SIM card. Cannot use mobile data.

The phone model is Xiaomi redmi 9t and is not Xiaomi redmi note 9t. I don't dare to open the phone. Thank you so much for the guidance 🙂

@joeycheng

Sorry about that. I've linked a teardown video for your model just so you can see what's inside.

One option to try if you want, is to cut a thin piece of paper exactly the size of the SIM card and secure it to the non contact side of the card and then insert it in the SIM tray and see if the card is now being detected.

Sometimes the card reader pins loose a bit of tension on the SIM card and the paper just thickens the card fractionally. In effect it brings it closer to the pins in the card reader.

Don't make it too thick as you don't really want to force the tray with the SIM into the phone

Thanks so much for yr patience, time, replies and the video.

Honestly I don't dare to teardown the phone.

The phone also fail to turn on after a reboot following updates, and the only way to get it to power on was by waiting for the battery to fully drain and then using a specific button combination while charging.

This happens consistently every time I attempt to reboot.

Do you know how to solve this problem? I’ve watched many videos, but it still seems to require a teardown of the phone and adding a solution to make it work smoothly.

So sorry, I don't quite get u. Cut a thin paper and secure it on the non contact side of the card?

Btw, do u think if factory reset will work? Thank you.

@joeycheng

You could try a factory reset but if it is a hardware problem that won't fix it.

If you do want to try anyway, backup the phone data to the cloud or a computer before doing the reset. Also if there's a Google account associated with the phone, make sure that you know the account user ID and password as this will be needed to setup the phone again once the reset has been done. When you factory reset the phone, all your data will be erased and the FRP lock (factory reset protection) will be enabled. This is a security measure against theft. Without the account details you will be locked out of the phone.

There are two sides on a SIM card, the contact side (examples) and the other side which usually has the service provider name etc.

It is the contact side that makes electrical contact with the SIM card reader in the phone so by adding thickness (thin paper - cut to match the size of the card exactly so it fits in the tray) to the non contact side, you are effectively moving the contact side of the card closer to the SIM card reader pins, hopefully making for better electrical contact in case the pins have lost a bit of tension, i.e. not pressing down as hard on the SIM card as before. Initially don't make the paper too thick as you still want to be able to remove the SIM tray from the phone with the card still in it.