oops! silly woman that i am has put wrong answer... deleted it.

connector no 2 is the digitiser, check it is on properly, clean of dust and not damaged. give it a good clean. also try a hard reset...press and hold home and power button until apple appears then allow to reboot. connector 3 is for earpiece and proximity...sorry for confusion, I'm getting old.

RE: the imei being possibly blocked.... you can do a quick search online.. the imei is printed on the sim tray (hopefully your tray is original to the phone) either for free which is often updated infrequently so is less accurate or pay a small amount to a site that gets updates daily/hourly which will be far more reliable. If you know the carrier then you could try contacting them directly. The serial number is printed on the metal shield of the motherboard if you are unable to get the imei and this may be more useful if you are contacting the carrier.

If this turns up ok then it may be the chip that is damaged.