I cannot use VisemeDriver Component

I would like to estimate visemes from audio in Unity.
I configured my project according to the documentation, but FaceExpression.AreVisemesValid is always false, and as a result, the VisemeDriver component does not work.

This issue also occurs in the Face Tracking sample scene included with the Meta Movement SDK.

Unity version: 6000.2.10f1
Meta Core SDK version: 81.0.0
Meta Movement SDK version: 81.0.0

How can I use the VisemeDriver?
Please let me know if there is a workaround or solution.