There is an issue with all of the "Bonded with ..." achievements in the Steam version of this game that has to do with a naming issue in the code in the end interview where these achievements should pop. NS Plover on Steam was able to get permission from the developers to create a mod that fixes this until the development team can get around to fixing it officially. Both the mod and a copy of the email (for those that want to see that permission was indeed granted) can be found on GitHub here:
https://github.com/SimplePatches/1931-Scheherazade---Bonded-...For Felix specifically, I recommend using the information on the wiki page to find all the points needed to get the achievement once you have the mod:
https://applesauce.fandom.com/wiki/Bonded_with_Felix