Joke Collection Website - Blessing messages - Card slot 2 can't use Unicom card, why?

Card slot 2 can't use Unicom card, why?

1. Whether the Unicom card has insufficient contact with the metal contact of the mobile phone; 2. Whether Unicom card is damaged; 3. Is the location a signal blind area or there is no signal suddenly. Tips: It is recommended to put Unicom card in other mobile phones for testing. If this situation still occurs, it is recommended to check the card in the business hall.