what does this code mean 0xE8000015?

Please check:

1.

Try to free up iPhone device storage see this Apple articles below:

If you need more space for an update on your iPhone, iPad, or iPod touch

If you need more space for an update on your iPhone, iPad, or iPod touch - Apple Support

How to check the storage on your iPhone, iPad and iPod touch

How to check the storage on your iPhone, iPad and iPod touch – Apple Support (UK)

Clear Other storage on your iPhone or iPad

Clear Other storage on your iPhone or iPad - Apple Support

-> What's the difference between device storage and iCloud storage?

What's the difference between device storage and iCloud storage? - Apple Support

2.

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.

Make sure your Windows PC is up to date & have the latest version of iTunes.

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

Check the Wi-Fi connection.

Turn Off Hotspot.

Turn Off or remove VPN if necessary.

Disable all AV & Firewalls temporarily while you restore your iPhone.

Update your Mac or Windows PC and your iPhone to current versions, update your iTunes to current if you’re using Windows, restart everything, and test again.