I want to share 2 files so I created 2 different .torrent using Tixati.

Add -> Create New Seed -> Protocol: V1+V2 -> DHT/PEX: Off -> Trackers (I add here the url the italian private tracker gives in its guide) -> Comments (I added a comment)
Then I added the file. Tixati uploaded the file in the GUI, then I did "share" -> "save .torrent" and I uploaded the torrent on the private tracker

Now if I check file properties I see these:

*** 28/03/2025 ***
[00:39:35]  loading complete transfer
[00:39:35]  info-hash set > ECC20380XXXXXXXXXXXXXXXXXXXXXXXX
[00:39:35]  v2 info-hash set > E142EC2E899XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
[00:39:35]  starting
[00:39:37]  seeding initiated
[00:39:38]  tracker announcing [started] > https://XXXXXXXXXXXXXXXXXXXXXXXX.XXX/announce/XXXXXXXXXXXXXX [v1]
[00:39:38]  tracker announcing [started] > https://XXXXXXXXXXXXXXXXXXXXXXXX.XXX/announce/XXXXXXXXXXXXXX [v2]
[00:39:49]  tracker error: Failed: InfoHash not found. > https://XXXXXXXXXXXXXXXXXXXXXXXX.XXX/announce/XXXXXXXXXXXXXX [v2]
[00:39:54]  tracker error: Failed: InfoHash not found. > https://XXXXXXXXXXXXXXXXXXXXXXXX.XXX/announce/XXXXXXXXXXXXXX [v1]

If I try Open File o Open Folder all works fine, Tixati opens the file and the folder. In the private tracker, I see my uploads as approved. So why this error?

I downloaded the .torrent from the private tracker and opened it with Tixati. I can see:

 *** 28/03/2025 ***
[01:10:56]  loading transfer
[01:10:56]  info-hash set > 279E1FB67XXXXXXXXXXXXXXXXXXXXXXXX
[01:10:56]  starting
[01:10:57]  downloading initiated
[01:10:58]  tracker announcing [started] > https://XXXXXXXXXXXXXXXXXXXXXXXX.XXX/announce/XXXXXXXXXXXXXX
[01:10:59]  tracker responded OK, returned=0  seeds=0  peers=1  interval=33:33  minint=30:00 > https://XXXXXXXXXXXXXXXXXXXXXXXX.XXX/announce/XXXXXXXXXXXXXX

So I see 2 different info-hashes, why?

I have on my pc the 2 torrent of the same file: the first is the one created by Tixati, the second is the one download from the site. They are different, the "local"/uploaded torrent is bigger (104 kb), the downloaded one is smaller (41 kb).

You can use Torrent File Editor or Bencode Editor to compare the contents of torrent files.

Most likely, your sharing community server doesn't support v2 files, and also automatically sets the private flag if it's not set, which changes the hash. It also usually inserts unique per-user tracker links on download.

Most often, the official guide tells you to download the torrent that was processed by the system, then seed the files.

v2+1 compatibility doesn't mean you'll get the same hash when creating a torrent in both v2+1 and v1, it just means that clients that support only v1 can read the information provided by it.
Also like Guest said, a private key will be added to your torrent, which is why you always have to re-download the .torrent file from the tracker, private trackers usually don't bother with implementing v2.

How can I add the private flag using Tixati when I create the torrent?