Restore iPhone 11

Hi there. My great aunt got a new iPhone. She’s old, and had no idea how to use it. She doesn’t even know it’s phone number nor the passcode she made to get in. So, I was going to reset the whole thing for her. I don’t know the passcode either so therefore I can’t get in. But, when I try to do a restore on my MacBook, it fails every time with an error message that says it failed due to a corruption during the download? I have no idea. Any help?