Apple - Can't restore or update IPhone - TATSU declined to authorize
Mac
If you're using a Mac, follow these steps:
In the Finder, choose Applications > Utilities.
Open Terminal.
Type this command and press Return:
sudo nano /private/etc/hosts
Enter the password you use to sign in to your computer and press Return. >You won't see text appear in the Terminal window when you type your >password.
Terminal displays the hosts file. If you don't see a window similar to the one below, make sure you're using a nonblank administrator password.
Navigate using the arrow keys and look for an entry containing >“gs.apple.com”.
If you don't see any entry containing gs.apple.com, then the hosts file >isn't related to the issue. Close the Terminal and move on to the next >section of this article, "Address TCP/IP filtering, firewall, or security >software."
Add the # symbol and a space ("# ") to the beginning of the gs.apple.com >entry.
Press Control-O to save the file.
Press Return when asked for the filename.
Press Control-X to exit the editor.
Restart your Mac.
After your computer is finished restarting, try to update or restore your >iOS device again.
https://support.apple.com/en-ca/HT201442
That being said, there is no such entry in my /private/etc/hosts or in my /etc/hosts file, so I will look for other solutions to this error.