1, try to restart the phone.
Restart the phone, and the phone will re-read the SIM card to see if it can be used again.
2. Check the phone settings to see if the SIM card is enabled.
Go to mobile phone settings-mobile network/dual card and mobile network-SIM card information and settings-click to enter the corresponding SIM card-enable the SIM card, and make sure the switch is turned on.
3. Check whether the SIM card is installed backwards.
Please refer to the card loading steps in the user manual to see if the SIM card is loaded in the right direction.
Go to Settings-System Management/My Devices-Customer Service-User Manual-Mobile Phone Overview and Quick Start-Installation and Preparation to learn how to install and remove the memory card and SIM card.
Entry Settings for Some Models-More Settings-User Manual/Instruction Manual-Overview and Quick Start of Mobile Phone-Installation and Preparation.
If it is a double-layer Cato model, you can take a look at this tutorial for installing SIM card: Web link.
Note: SIM card 1 and SIM card 2 are installed in the same way.
4. Check whether the SIM card looks good.
Observe whether there are stains on the metal surface of the SIM card, and clean the stains on the surface of the SIM card to avoid the SIM card from being unrecognizable due to poor contact. If the cut SIM card is used, the shape of the SIM card may be nonstandard, resulting in poor contact and inability to identify the SIM card. It is recommended to go to the operator's business hall and change to a standard SIM card.
5. Dual telecom cards need to use VoLTE network.
If two telecom cards are used at the same time, the secondary card (non-data card) needs to open the VoLTE service and be within the coverage of the VoLTE network before registering the network.
6. Cross-validation.
Please install the SIM card on other devices, or install other SIM cards on the mobile phone for comparison test to determine whether the SIM card is faulty. If there is a problem with the SIM card itself, it is recommended to replace the SIM card in the operator's business hall.
7, the influence of 2G/3G network withdrawal
At present, the operator's 2G/3G network is gradually withdrawing from the network, and the use of 2G/3G network by some models of supplementary cards may be restricted.
8, service center testing
If the above methods fail to solve the problem, please back up the mobile phone data in advance, and bring the mobile phone and purchase voucher to the vivo customer service center for testing (address of customer service center: go to vivo official website /vivo mall APP-My-service outlets/after-sales outlets-select provinces and cities to check the address of customer service center).