Synonyms that are in the dictionary are marked in green. Synonyms that are not in the dictionary are marked in red.
Antonyms that are in the dictionary are marked in green. Antonyms that are not in the dictionary are marked in red.
If that still doesn't work, then it's possible that you may need to update the drivers on your computer or reinstall the Kobo Desktop app.
Source: https://www.devicemag.com/kobo-ereader-not-showing-up-on-mac/