We have a documented issue we are currently working with Apple Support to try and resolve. Until then here is a work around for the issue.
It seems if a user checks out a Library Loaner iPAD creates a passcode as well as enters in their iCloud credentials, Apple Configurator will not be able to refresh/reimage the iPAD and will display this error "Unable to send RequestUnlockToken command to device"
Most common reaction might be to try again by unplugging and replugging to re-initiate the refresh but this will only produce a different error "Could not restore backup" it will continue to produce this error if you keep trying
To get around this error please try the following:
- Confirm the device producing the error is selected
- Once selected, press "Clear" near the top right of the window
- This will then get you back to the main page, you can now manually press "Refresh" near the bottom
- The refresh should go rather quickly if there are no new or updated apps to be installed. After it is done refreshing it should be good to go, but you can confirm by checking there is no passcode and there is no user credentials still entered in the device.
Here is a screencast showing the issue and workflow to get around it
PW: Get past the lock issue
Cannot Refresh Library Loaner iPADS properly