Possible reasons why Apple's mobile phone can't read SIM card:
The first method is to turn on the flight mode of the iPhone, wait for more than ten seconds and then turn it off to see if you can read the Sim card.
The second method is to shut down and restart the iPhone, and see if the Sim card is valid after booting.
The third method, if the above two measures fail, then back up the iPhone and restore the factory settings.
The fourth method is to take out the card with a card-taking needle to see if it is offset, then adjust it and put it in to see how it works;
The fifth method is to check the update of operator settings.
Operator setting update is a small file (about 10) installed on iPhone or iPad(WLAN+ cellular model).
Kb). Operator settings include APN, MMS settings, network updates, and default applications such as stock market, maps and weather. You may receive periodic notifications about installing updates to operator settings. After networking, you can enter "Settings-> General->; About this machine "check for updates.
The sixth method is to verify the SIM card, take out the SIM card and verify whether it is a valid SIM card manufactured by the operator. Then check for damage, wear or other faults before plugging the iPhone back in.
The seventh method, brush machine.
When updating the system, check "Keep user data refreshed" when refreshing. After refreshing, mobile phone data such as songs, videos, address books, photos, calendar information, etc. are still there, but it is best to make a backup operation before restoring.
If all the above methods don't work, it is likely that there is something wrong with the hardware of the iPhone, which needs Apple's after-sales inspection to solve.