By hard restart I assume that you mean the forced restart like this. To force restart your device, press and hold both the Sleep/Wake and Home buttons for at least ten seconds, until you see the Apple logo.
Make sure that you are running the latest version of iTunes and that your computer is fully updated as well. Plug directly into the computer and don’t use a hub.
If you see an error when you update or restore your iPhone, iPad, or iPod - Apple Support
If you are fplowing all of the steps here, If you can't update or restore your iPhone, iPad, or iPod touch - Apple Support, and it still doesn’t work, contact Apple support here as stated at the end of the support article.
If you can’t update or restore your device with recovery mode, or you can't use recovery mode because of broken buttons, contact Apple Support.