While I'm testing unit behavior with dasilvarsa proposals, I recoled that I'm doing and other trick to connect to PC.
When I'm desperate and do not want to use Clear NonVol or to play again with PC drivers I'm doing the following:
I'm entering in preboot mode and do nothing. Unit itself is not connected to PC.
System disappears and after that unit reboot. Usually it works, but not always.
You may try it too.