Why can’t iPhone text messages be backed up?

Press both buttons together to restart the phone;

2.

The first step is to prepare the backup, the second step is to start the backup, and the third step is the program Synchronization preparation, step 4 is to synchronize the program's mapping file, step 5 is to start copying the program to your mobile phone;

3.

Your problem lies in the second step. Then it means there is a problem with your iPhone system file. Apple cannot recognize the correct backup file, so the boot cannot be completed.