1, first look at whether the sim card is inserted backwards, or inserted in the wrong position, adjust to the correct position to insert it can be solved.
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2, and then see if the sim card board is deformed and damaged, resulting in poor contact of the sim card can not read the sim card, you can replace the sim card or repair it.
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3, you can also check whether the sim card is damaged, you can let into other mobile phones to try, if other mobile phones are still unable to use, but you can read other sim cards, it is clear that the sim card has a problem, you can go to the sim card company to replace the new card.
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4, the other is to see if there is a debt or bad signal situation, if this problem is timely recharge or wait.
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5, there is also a case that the phone may be damaged, resulting in the sim card can not be read, you can directly go to repair, mobile phone damage can only find professionals.
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6. If it is not the above problem, it is generally the setting problem, click [setting]; In the displayed interface, click the \"Mobile Network\" option; Click on the \"Carrier\" option inside; Turn on automatic registration, so that you can automatically select the sim card carrier, ensure that the sim card can be used, or wait for the detection phone to select the right carrier, so that the sim card can read
First confirm that the card is no problem, if it is a mobile phone suddenly like this, you can try: remove the battery, hold down the power button for 5 seconds, and then install the battery, start.