I just installed 64-bit tixati on Windows 10 and clicked on a magnet link in Opera 43.0.2412.0 64-bit. Opera asked if I wanted to allow it and I did. Then, it loaded up tixati. But, nothing happened once tixati loaded up. Same behavior in Firefox. That might have something to do with the link itself, but it does get passed to tixati like it's supposed to.

I checked. tixati does a key at

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\magnet

along with

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\magnet

and

HKEY_CLASSES_ROOT\Magnet

I see

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\tixati.torrent HKEY_CURRENT_USER\SOFTWARE\Classes\tixati.torrent HKEY_CLASSES_ROOT\tixati.torrent

which are referenced by

HKEY_CLASSES_ROOT\.torrent HKEY_CURRENT_USER\SOFTWARE\Classes\.torrent HKEY_LOCAL_MACHINE\SOFTWARE\Classes\.torrent

There's also:

HKEY_CURRENT_USER\SOFTWARE\Classes\tixati.torrent HKEY_LOCAL_MACHINE\SOFTWARE\Classes\tixati.torrent

So, I would reinstall tixati just for good measure. You might even want to remove any of its registry keys after the uninstallation before reinstalling.

If that doesn't help, download the Opera installer, launch it, click "options", set "install path" to a folder on your desktop, set "install for" to "Standalone Installation (USB)" and install. Try magnet links in that Opera. If they work there, it means it's something messed up with your Opera profile (mabye Local State file or preferences file).

I didn't try in Opera 41/42. So, if it's a bug, maybe it's just fixed in 43.