My iPhone 5s is stuck!

I get this error:

The iPhone [device name] could not be restored. An unknown error occurred (9).

Before I take it to the Genius Bar I'm wondering if anyone has any ideas. I've googled and tried all the suggestions on this page https://support.apple.com/en-us/HT201444

Things I've tried:
  • Different cables
  • 3 different macs
  • holding down home and sleep/wake