Little Snitch 6.0.4
Objective Development has released Little Snitch 6.0.4 to fix a bug that prevented existing rules and settings from being preserved when upgrading from version 5 to version 6.0.3. If you were affected by this bug, you can restore your previous rules and settings by choosing File > Restore from Backup from the menu bar in the Little Snitch app. Additionally, you can find a backup file of your Little Snitch 5 configuration in the /Library/Application Support/Objective Development/Little Snitch folder. ($59 new, $39 upgrade from previous licenses, free update, 36.4 MB, release notes, macOS 14+)
Yep it happened to me rules were basically erased when going from 5 to 6. But with the help of the objective development team they put me on the right track, and then about 5 days later the 6.0.4 version came out. If I only waited!!