One of the reasons may be that the ip address is automatically obtained incorrectly.
Because the SIM card has a chip inside, it is possible that the sudden failure of the SIM card chip is damaged. Generally in this case, take out the SIM card to another mobile phone to try, or take someone else's SIM card to try on their own mobile phone, you can determine whether it is really a SIM card problem. If there is really a problem with the SIM card, go to the operator to replace the SIM card.