@monkeybutler,
This error indicates that calibre is unable to communicate with your iPad.
Some users have reported that restarting their computer and resetting the iPad resolves the problem.
Try the following steps:
- Exit calibre, disconnect your iPad
- Reboot your computer
- Do a hard reset on your iPad by holding the Home button and Power button together until you see the Apple icon, then release the buttons
Try connecting again.
If that fails, then create an issue at the GitHub issue tracker as described in the If you have problems section of the first post in this thread.
G