Hi there Carrob7,
I saw your post about the language selection issue you're seeing on your Mac, and I'll be happy to see if I can help. The Dictionary app is a great tool.
To verify, you're able to check the boxes next to the Italian and Italian-English dictionaries, but they don't seem to find anything. Is that right?
Which exact macOS version are you using under Apple menu () > About This Mac?
Does it help if you click Apple menu () > Restart and test it again?
If not, try booting your Mac into safe mode to test again: How to use safe mode on your Mac. Once in safe mode, see how it works, and then restart to get back to normal mode.
I also recommend creating a temporary administrator account, and then testing for the same behavior there. This will help to determine if you have a system-wide or user account-specific issue: How to test an issue in another user account on your Mac
Feel free to reply back with the results of those tests!
Kindest regards.