When using roaming SIM cards, inevitably we find ourselves eventually running into those evil “Invalid SIM card” errors or “please insert SIM” even though the SIM card is already in the device. No matter the device — be it Android, iPhone, Windows Phone or BlackBerry — it’s bound to have these issues from time to time.
Many times, dropping or bumping the phone will knock the SIM out of alignment or the SIM could have simply failed to load. The most common way to fix the most common errors is by simply turning the device off and removing the SIM card. SIM cards are usually located beneath the battery or via a SIM card slot on the side of the device.
Once the SIM is removed, it sometimes helps to clean both the SIM card and where the SIM connects (if you can reach it) with a pencil eraser. Be sure to inspect the SIM card for signs of damage before and after you do this to make sure there aren’t any scratches or dings that might inhibit the card’s usability.
Re-insert the SIM. Be sure to insert the SIM card with the gold bands facing down and push until the SIM clicks into its slot. It’s possible that the aforementioned errors occurred due to the SIM being inserted improperly or not being pushed in all the way.
Try turning the power back on to see if the errors have been resolved. If not, it’s possible that your SIM is incompatible with your device. Check with your service provider to ensure the SIM and your device are compatible. Each SIM contains different carrier software; your service provider will be able to configure your SIM.
Another common issue (since we use unlocked devices with our international SIM cards) is the PUK (personal unblocking key) code was inserted incorrectly. You’ll have to talk to the service provider from which you obtained the device to make sure the PUK code is correct (and, of course, make sure the device was unlocked).