Q：There are two SIM card slots, one of which is not working.
A：1. Are both SIM cards installed correctly? (Refer to the instruction manual.)
2. Are the SIM cards damaged? Is there severe oxidation on the chip that prevents them from being recognized?
3. Is the SIM card a standard Nano card? If it's a hand-cut card, it may cause poor contact in the card slot, resulting in the card not being read. It is strongly recommended to replace it with a standard Nano card.
4. Swap the two cards in the card slot to see if they can both be detected. If they still cannot be read in the same slot after swapping, the card slot may be damaged.
5. After correctly installing the SIM card, turn off and restart the device to see if it can recognize the card. If it still cannot be read, refer to step 3 to determine if the card slot is faulty.
