iphone cannot be restored.

Yes, I got very scared when this happened to me.

however this worked for me:

try a dfu restore:

1. Connect the device to a computer using a USB cable.
2. Quick-press the Volume Up button
3. Quick-press the Volume Down button
4. Hold down the Side button until the screen goes black, then hold down both the Side button and Volume Down button.
5. After 5 seconds, release the Side button while continuing to hold down the Volume Down button. 

• • If the Apple logo appears, the Side button was held down for too long.
  • Nothing will be displayed on the screen when the device is in DFU mode. If open, iTunes will alert you that a device was detected in recovery mode. 
  • If your device shows a screen telling you to connect the device to iTunes, retry these steps.

then, on iTunes, click Restore iPhone and try again.

this is apple’s guide to restore errors too: https://support.apple.com/en-us/HT204770

Do you have a backup? If so, use this. Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

If not, try these:

If you can't update or restore your iPhone, iPad, or iPod touch - Apple Support

Restore your iPhone, iPad, or iPod to factory settings - Apple Support

Have you tried this? --> If you see error 9, 4005, 4013, or 4014 when you restore your ...