This prompt appears, indicating that there may be a problem with the modem of the iPhone cellular mobile network. If you restore or erase the data on the iPhone at this time, you may not be able to activate the device, so this operation is not recommended. Please contact Apple's official after-sales service for maintenance.
To manually check whether there are operator settings updates and install them, only wireless operators can access and manage account-related details. If users need help finding the service page of wireless carriers, please refer to the Apple Carrier Support article or use the online search engine. If the operator confirms that there is nothing wrong with the user's account or network, but the user still cannot connect to the cellular network, please contact Apple Support.
Extended data:
Precautions:
The cellular network connection on the iPhone requires the SIM card provided by the operator. Please contact the user's operator to set the mobile phone number.
IPhone can use nano-SIM card to access carrier network. On the iPhone that supports dual SIM card function, you can use nano-SIM card and eSIM (not available in all countries or regions).
In some countries or regions, some iPhone models support dual SIM card function using two nano-SIM cards.
Apple support-if you watch it on iPhone or iPad.
Apple Support-Set up cellular network service on iPhone
Baidu encyclopedia-cellular network