HP PRIME horribly bricked during update ? (SOLVED!!)

[ytterligare]

I write here the solution, so that maybe someone else in the same situation, can understand the steps to solve the problem.

I found a post on a forum, written by one of the head developer of the Prime project : to solve another problem ( partial update ) he suggested to press "Symb", press the button on the back with a pin, and release the pin.

It WORKED !! I was able to return again in Recovery mode (v13).

At this point I tried at least three times to update the Prime but the result was always a final black screen and a calc that didn't turn "ON"...
Changed USB port and reboot...again update but same result.

At this point, I changed PC, and did the same update process and...after the update, instead of staying black, the Prime booted up with the initial setup !!

I think something on the first PC USB's was preventing a final "acknowledge" to the Prime, so that the process was truncated prematurely after copying the three files that are part of the new firmware.

Changed PC, and everything went smooth.

Sorry for bothering you all people
Goodnight
Andrea