Iphone 6s Plus restore

Troubleshooting:

Turn your iPhone On and unlock it -> enter the passcode.

Go to Settings -> set Auto-Lock to Never.

Connect your device to your computer using an Apple USB cable & try also another USB cable.

(macOS) Make sure your Mac has the latest version of macOS 

(Windows OS) -> Make sure your Windows PC is up to date and Update to the latest version of iTunes

Update to the latest version of iTunes for Windows 10 – Apple Support (UK)

See also -> Check your third-party security software.

Check the Wi-Fi connection.

Turn Off Hotspot.

Turn Off or remove VPN if necessary.

Check VPN (Virtual Private Network) and third-party software to help resolve network connectivity issues

Check VPN (Virtual Private Network) and third-party software to help resolve network connectivity issues - Apple Support

Disable all AV & Firewalls temporarily while you connect the iPhone.

I have an error code 5 while trying to restore an older Iphone 6s Plus?

The problem is it doesnt want to switch on. If I try and switch on the phone it goes immediately to the screen that shows plug into computer and shows support.apple.com/iphone/restore.

Get support from Apple directly -> Get Support or call Apple in your region see -> Contact Apple for support and service or check -> here for more support and assistance.