I am having the same issues. I have tried everything I can think of...I got it to work with one device unsupervised and I got it to work with one device supervised following theses instructions:
First, open Configurator and go to Prepare. Leave the device name blank, and turn Supervision on. Do not select any other options or any profiles. Hit Prepare and connect a device. Once it runs through the process and the device is Supervised, then manually go through the activation process until you finally reach the Home screen on the iPad. Now, in Configurator, go to the Devices menu up in the Menu Bar, and choose Backup. Save a backup of this device. Once this is done, we can UnSupervise the device through Configurator which will restore it to factory defaults. Once done, unplug the cable from the device.
Now, go to the Prepare tab, choose your naming scheme for the devices, and turn Supervision on. Leave iOS set to Latest, and for Restore, make sure you choose the backup we just created. For Profiles, select your wireless and enrollment profiles. Hit the Prepare button, and connect your device. What will happen is the backup will be restored, and the wireless and enrollment processes will be completed, leaving you with an active and fully enrolled device. Any additional devices connected will follow the same activation process.
However, I am trying this with 8 devices as a beta test for an additional 250 devices. I still cannot reach multiple devices at once with any acceptable percentage of success.