You don't say what camera you're using, but it's a good bet that those features are available only in certain modes. Check your user manual; there's usually a table showing which features are available in which modes.
One thing you can't blame is your lenses. The ones you mentioned are fine. Quite a number of us have them both.
Sorry! Canon C300 mk ii.
I've read through the manual and made sure everything is as it should be. I've also done a bunch of different combinates of options in order to activate the Face Detection and Tracking.
It's probably something I'm just over looking, but it's strange that Face Detection and Tracking is the only thing that is greyd out under the Focus menu.
There area few settings inside the camera that once activated, won't allow face detection to be used. I can't recall the specific settings, but the camera will warn you of the consequences of chnaging certain settings.
Since I had just gotten the camera, I wasn't attached to how I had the camera setup. So the easy solution was to reset everything to factory settings.
It worked. I use my face detection all the time now.