idevicerestore -c "Unlock_Hub_iPhone7Plus.ipsw" Note: You cannot use standard iTunes for custom IPSW files.
Once booted, the custom IPSW will likely install a jailbreak (palera1n) automatically. You will then open an app called "Unlock Hub" or "Carrier Bypass" on the iPhone. unlock hub iphone 7 plus custom ipsw download
A: Your baseband did not flash correctly. Re-run the process, or downgrade to iOS 14 using a signed IPSW. idevicerestore -c "Unlock_Hub_iPhone7Plus