Help Rtorrent-pro won't open in QTS due to browser error.

[ramb13r]

I click on Rtorrent-pro icon in QTS and new Firefox browser tab opens with error.

I've cleared cache, refreshed, disabled Enhanced Tracking Protection, made pop-up exception, updated QTS, and restarted QNAP.
Similar error occurs in Vivaldi and Edge browsers.
Please advise how to fix browser error. Thank you!

 

[Silas Mariusz]

Does it also happen when changing port from 6008 to 6009?

Is this fresh rtorrent installation?

 

[ramb13r]

Error does not happen on port 6009. Thank you, Silas!
This was not a fresh rtorrent installation. I installed latest rtorrent over an old version from a few years ago.
Then I got a "no connection to rtorrent" message, so I tried restarting using "/etc/init.d/rtorrent.sh restart".
I got lots of chown errors, so I restarted QNAP. Now everything's ok.
Thanks again!