Same thing happened to me the other day. 'Reset LibreELEC to defaults' is the only way
First create a backup of your Kodi settings in LibreELEC (it will be stored in /storage/backups)
Copy the back up from your Chromebox to another device
'Reset LibreELEC to defaults' HARD RESET
after boot copy your back up to the chromebox /storage/backups
restore from backup
and you're back in business