Why Does My iPhone Say No SIM Card Is Installed?by Carol Finch
If you see an error message that no SIM card is installed or that the SIM is invalid, your iPhone can't recognize the card, leaving you without a cellular connection. This may happen with a new SIM or an existing card that has worked correctly in the past. The source of the error may not be immediately obvious, and can be due to a connection problem, a faulty SIM card, or outdated iPhone or carrier software and settings. Try troubleshooting the connection, SIM card and iPhone to try to fix the problem.
Check the iPhone's Connection
The iPhone may not recognize a SIM card if you have connection problems. To refresh settings and reconnect, put the iPhone in Airplane Mode.
Tap Settings and then Airplane Mode to turn off the iPhone's connections.
Tap the Airplane Mode button again to disable the setting and wait for the iPhone to reconnect.
Test the Sim Card
Open the SIM card tray on the side of the iPhone. Use the SIM eject tool that came with the iPhone, if you still have it, or open up a paperclip and insert one of its ends in the hole to eject the tray.
Remove the card and check it, and the tray, for dust or damage. The card has a clipped corner, which should line up with the clipped corner of the tray. Make sure the card sits flush in the tray before you reinsert it.
If this doesn't work, you can test the card if you have, or can borrow, another SIM card or iPhone. Try inserting a different SIM card in the iPhone. If it works, the original may be faulty, and you should contact your carrier. Alternatively, try inserting your SIM card in a different iPhone. If it doesn't trigger the error message, the card itself may be fine, and you should focus on troubleshooting the handset.
Restart or Reset the iPhone
Try restarting and resetting the handset to see if this refreshes the system and allows the iPhone to pick up the SIM card.
Press and hold the iPhone's Sleep/Wake button until it shows the power slider. Swipe this off, wait for the iPhone to turn off and press Sleep/Wake again to restart. If you still see the error message, press and hold the Sleep/Wake and Home buttons. When you see the Apple logo, release the buttons and the iPhone will reset.
Check for Updates
You may see SIM error messages if carrier settings or the iPhone's operating system are not up to date. Connect the iPhone to iTunes. If updates are available, you see a message when the handset connects. Select Download and Update.
Check for iPhone operating system updates, even if they don't appear when you connect the iPhone. Select the iPhone's icon in iTunes and then Summary.
Look in the iPhone's summary area to see if it needs updating; if it does, select Update. If the message says software is up to date, select Check for Update to double-check for updates.
Reset Network Settings
Resetting network settings may help the iPhone pick up a SIM card by clearing network connection problems. Before you take this step, make sure that you know passwords for your current networks. After the reset, you need these passwords to rejoin networks.
Tap Settings and then General. Tap Reset.
Tap Reset Network Settings.
Enter your iPhone's pa sscode, if you use one. Tap the Reset Network Settings confirmation message.
Wait for the iPhone to restart and reconnect.
An iPhone sometimes shows SIM error messages after water damage. If the handset has recently been in contact with water, this may be the source of the problem and you should dry out the iPhone.