Solutions:
After confirming the mobile phone model and SIM card type are the same, if it doesn't work, the following method can be used to check:
1. Enter "* # 06 #" on the dial-up keypad to check the phone's IMEI number to see if it is normal. If there is no IMEI number, it is suggested to directly go to the MI authorization service center for inspection.
2. Re-install the SIM card (please note: 1. Whether the SIM card chip is oriented correctly, there will be a diagram showing the placement method of the corresponding SIM card,2. If the orientation of the SIM card is correct or not, remove the SIM card, wipe the metal chip area of the SIM card with rubber or alcohol, and try again.
3. Enter *#*#64663#*#* into the dialing interface to enter the hardware detection, select "SIM card detection", and check whether the SIM card state is inserted.
A. If no SIM card is displayed or the SIM card is not inserted, try to replace the SIM card, but the SIM card still cannot be detected. If the SIM card is guided back to the factory or machine, it will still be invalid and led to the MI authorization service center for inspection.
B. If it can be detected after replacement, it is judged to be a SIM card fault. Please replace the SIM card and try.
4. If none of the above methods can solve this problem, it is suggested to go to MI authorization service center for inspection.