Thanks Merlin,
Could you please explain what does booting with WPS button do exactly and what is the correct procedure? I would to add that info to the very beginning of this thread (where I described recovery procedures)
Booting with the WPS button pressed means the router will wipe out nvram at boot time. This does not always work with the AC56 however, sometimes the CFE is unable to properly parse the current nvram content, so it won't be able to configure the Ethernet interface, or read for the button states.
When that happens, you have to connect a serial cable to the router's internal header, and turn the router on while you keep Ctrl-C pressed on your terminal. There is a VERY small window of opportunity then for the CFE to stop the boot process, and give you a CLI where you can manually erase the nvram.