IPhone says no SIM card installed

HI I HAD THE SAME PROBLEM AS YOU, go to settings then reset network settings and after that enter the network, I hope this helps you otherwise you can unlock it again with ultrASNOW.

Hello everyone
I have an iPhone 4s that was working perfectly, but unfortunately it no longer detects my SIM card. It doesn't ask for the PIN code and it stays on "searching." I've tried everything, but nothing happens.
Thank you in advance.

Hi, I also had the same problem and I just removed the SIM card without turning off the phone, then it detected it. I entered the unlock code and there you go.

Hello to you,

I just had the same problem just now, and being the brute that I am, I got annoyed and I twisted (very, very slightly) the card holder so that the SIM circuit would stick to the phone, and I turn it on "SIM card locked" => unlock :)

I've had the same problem and now it's perfect, I can pick up my SIM card network, so just connect the iPhone to iTunes, then go to Settings == General == Reset == Reset Network Settings and everything will be fine (the iPhone must be connected to iTunes).

You need to open it, and under the SIM card tray, there is a small copper wire.
When the card tray is inserted, it should push the copper wire so that there is no contact.
If it does not, you need to raise it a little, but be gentle.

I sent the iPhone to two repair shops, and after a few months of waiting, I decided to try it myself, and here I found the problem and even fixed it.

Good luck!!