This is to show you how to fix default credentials not working in qbittorrent in truenas core not sure whether it will work in scale
first open a shell to the qbittorrent jail you created
then stop the qbittorent service using the following command
service qbittorrent stop
vi the config file
vi /var/db/qbittorrent/conf/qBittorrent/config/qBittorrent.conf
Add the following line at the end of the file
[Preferences] WebUI\Password_PBKDF2="@ByteArray(ARQ77eY1NUZaQsuDHbIMCA==:0WMRkYTUWVT9wVvdDtHAjU9b3b7uB8NR1Gur2hmQCvCDpm39Q+PsJRJPaCU51dEiz+dTzh8qbPsL8WkFljQYFQ==)"
Finally start the service again
service qbittorrent stop
Once you login make sure to change the password from the webUI
When i did this i uninstalled and reinstalled the plugin