Download and Install Tool in macOS
Download here: https://mega.nz/folder/M9wDDbQC#Yz3Gnsdj_N2FbVrKdaKcnw

Restore device Fresh with 3uTools or iTunes or Apple Configurator2

Download latest iOS from ipsw.me

Note:
1. Dont do user data retain flash
2. Dont use service on “Unable to Activate” or “Baseband Issue” device.

Connect device to Wifi and let in “Activation lock” screen

Open Tool and Click “Boot”

After Successful Boot Navigate to Website

Register Your Device with Serial Number

Activate Device

Enjoy