I also experienced Apple Configurator 2 failure. Already I prepared DTK to be in "DFU" mode (checked LED turned orange). After I connect DTK with USB-to-C Cable (iMac - DTK Mac mini), Apple Configurator 2 does not show any device(supposed to be the DTK device) but show 'Apple Controller' (State Booted, I guess, it is the cable)... So, although I put 'UniversalMac11.020A5395g_Restore.ipsw' file to Apple controller and push 'restore' button, it fails withe the message. The System cannot be restored on this device. Can't restore device in this state - please reboot into Recovery orDFU.. I think the problem is 'Apple Configurator 2' cannot acknowledge the DTK device even though it turned to DFU... How can I checked if the DTK device in DFU mode? I checked with the LED color (orange : DFU mode), right? or Is this issue originated from the cable?? I hope to know....