Re: why is my samsung gts520 saying no sim mode
The SIM could have gone bad, the SIM port could have gone bad, the motherboard could have gone bad, the operating system could have gone bad ... It's not something we can guess at. Try turning the phone off, removing the SIM card, rubbing the gold contacts gently with a soft cloth, replacing the card and turning the phone back on. If that doesn't fix it, it needs to go to your carrier to check the SIM card and if that's good, to a repair shop.