Chosen Solution
It’s really weird, the phone works perfectly, connects to WiFi and runs as well as it can. The only issue is, when I insert the SIM card, it instantly comes up with an icon showing that it can’t find a network. When going into the SIM settings, it clearly can recognize that it’s an AT&T SIM card, but it can’t find the network. This SIM card works on my iPhone and my Android. I’ve tried other SIM cards in the Lumia and it does the same thing, recognizes the carrier but won’t find a network. Does anyone know what could be causing this?
Hi, Has it worked OK before with that SIM card (or any other card)? I don’t know the phone but was wondering if there is an antenna problem with the phone. The phone would recognize the carrier because that information comes from the SIM card so at least it proves that the SIM reader in the phone is alright, to a degree anyway. I realize that you said that the WiFi works OK but looking at this link it shows that there are two antennae in the phone. Perhaps both need to be connected and functioning for best connection to mobile phone and WiFi and one may be loose etc. Worth a look anyway. Here’s a link to the ifixit Microsoft Lumia 640 XL Repair guides which may be of some help.
