The hardware, if you have it lives behind the front bumper.
I understand that early Model S with the centre grille have the wiring but not the Home Link transponder.
If you have an updated Model S or a Model X, so far we only have a 2018 Model S owner confirm that it works.
I speculate that Tesla has rewritten the code to not show the Home Link icon unless it detects the transponder but until more people dig behind their front bumper we’ll never know.
I’d love to know the part number for the transponder on late model cars so I could order one, may have to headlock the service manager at Alexandria to get it out of him when I am there on Wednesday.