There are feedbacks on (1.1) Lenovo's website from consumers, and (1.2) Microsoft community, on above problem. 1 possible solution from Microsoft's community, and Lenovo's website, is about "Pinching" or "lightly pressing with thumb and finger" on screen frame (bezel) area around the webcam.
It could be a hardware issue; eg. wire connector, etc; not software problem, especially when Device Manager shows webcam is still working.
I did as suggested, and solved my webcam problem, which caused no video after every Windows 11 update. I encountered this issue since Year 2022, for almost every Windows 11 update.
I attached a picture as reference; take note red colour rectangular box around webcam. This is the area to "pinch".
Note :
- I download a Lenovo notebook picture online while writing above.