If you saved the file once, LightBurn might have saved a backup file next to it.
If not, you should be able to recover settings by loading a ‘preferences’ (aka ‘prefs’) file.
In LightBurn, click File, wheel down and click ‘Load Prefs Backup’ ( It’s right near the bottom of the list. )
Select a backup file from the approximate time when it was working to your satisfaction.