How to display the phone book by viewing SMS, and why?

You really can't rule out the possibility that the slot is loose. Think about how many needles are in the card slot. Is there any situation that poor contact or broken pin affects the registration of SIM card but does not affect the reading of information?

From a technical point of view. Display invalid SIM card. There may be 2:

The SIM card information in the 1. home location register has been deleted. So I can't register to the network, which is obviously not the reason.

2. Authentication of SIM card However, the so-called authentication is a security mechanism for registered users (SIM) in the network. Only by comparing the values calculated by the home location register with those calculated by the mobile phone can they be registered in the network. If you change your mobile phone and return it, and it hasn't been moved before and after the change, you can basically rule out the problem of network authentication. However, the probability of such failure is quite small.

According to the above analysis, it is probably your mobile phone. At the beginning, I said that I could not rule out the possibility that the card slot was loose. If it has been used well before, the problem of card slot matching can be ruled out. Another possibility is that the communication module of your mobile phone may be damaged. The communication module has a wide range, which can be a chip for sending and receiving letters, a processor for calculating authentication, and so on. Specific testing needs to go to the mobile phone after-sales point.