Do you have access to a or a custom recovery like TWRP?
Attempting to downgrade from Android 8.1.0 (Oreo) to Android 7.0 (Nougat) or 6.0.1 (Marshmallow) without updating the modem files frequently breaks the EFS structure. Symptoms of a Corrupted EFS Partition j710f efs file
This comprehensive guide explains what the J710F EFS file is, why it gets corrupted, and how to safely restore it to bring your device back to life. What is the EFS Partition and the J710F EFS File? Do you have access to a or a custom recovery like TWRP
adb shell su dd if=/sdcard/efs.img of=/dev/block/bootdevice/by-name/efs Use code with caution. Reboot your device. 5. Final Checklist why it gets corrupted
Understanding the J710F EFS File: How to Backup, Restore, and Fix Network Issues
The software controlling the phone's radio communication.