Face not being detected ARCore

I have added ARCore to an empty project and after adding AR Session and AR Session Origin objects, and after clicking build and run, I can render a cube in AR (on the phone screen in real life) and it seems to behave properly (looks like it is in the real world not just rendered onto the canvas).

However, when I try to implement the face tracking, it does not seem to detect a face. I have added an AR Face manager script to the AR Session Origin gameobject and created a default AR Face Prefab, assigning it to the face manager. I have also assigned the AR Camera as the main camera if that matters.

I am using a samsung galaxy s8. I am exporting as a development build and USB debugging is enabled. I also made sure the save and include the scene in the build settings.

Edit: I have tried plane detection too and it works.