the file is hashed once during the torrent creation, and your existing copy is re-hashed to check if it is 100% the same file byte for byte. the problem is that, with time, this file sitting in your disk can have its content changed. that can happen because an app added, changed or removed part of its metadata, or it could have been corrupted during a backup, etc.

even if the file plays perfectly, if the hash has changed the slightest, it cannot be re-seeded.
in a case like this, if you look up on the site and cannot find an existing copy of the file in another torrent, you can re-upload it.

I looked at this one on the tracker. Your qBittorrent is connected and announcing fine, but it reports 0% done, so it counts you as a leecher, not a seeder. ianfontinell is right: the client has not found your copy of the file. A seeder only shows up once the client has checked the data and reports 100%.

For this torrent the client expects exactly one file:
BrokeStraightboys - Blake Ellis & Ryan Pitts.mp4 (823,283,174 bytes)

What to do: in qBittorrent use Set location and point it at the folder that holds the file (not at the file itself), make sure the file name matches exactly (rename your copy if needed), then right click and Force recheck. If it then shows 100%, you are seeding. If the recheck stays below 100%, your copy is a different encode or cut and cannot seed this torrent.

The leechers you saw are not online right now, so even at 100% it can take a while until someone pulls from you. Thanks for helping with reseeds!

Joker

torrent shows as stalled because the client never recognizes the file you are trying to point it to, it is trying to download a file with no seeders so it stays stalled indefinitely.

check if the file name and path are both correct, if everything is right the status should be 100%.