That tracker URL is missing your passkey and that is the reason why the tracker returns "Failure: unregistered torrent pass"
The URL just above includes the personal secrete passkey and that is why it displays working (in funzione)
You've got tow possibilities:
1/ just ignore that failure, it doesn't harm
2/ right mouse button click on that tracker URL and select "Remove tracker" from the drop down list. Then only the working tracker URL remains listed and the error is gone.
Remark: When you create a .torrent file, you'll usually do that without your secrete passkey. µTorrent is default to start seeding once created a .torrent file. That is good for public trackers without passkey system (e.g. The Pirate Bay). However on private trackers, that is the wrong way and should be deselected. Not having deselected it can explain why you got that tracker URL without the passkey in that torrent details.
Then when you re-download the small .torrent file from GayTorrent.ru, it will have the passkey inserted. You must have done that, because the other URL got your passkey.
This principle:
Create a torrent.
Upload it to the tracker.
Re-download it from the tracker (to have the passkey inserted).
Add to the torrent client
and point the download to the directory with the file from which the torrent was created,
is typical for all the private trackers I know
