What this is
- A strict logged-out (Firefox Private Browsing) reproduction of YouTube embed failing for video id 3L3mhFuspZI.

Expected
- The embedded player loads and plays normally.

Observed
- The embed URL renders: "Video player configuration error" and shows "Error 153".
- Screenshot includes the browser URL bar and the on-page error label.

Environment
- Browser: Mozilla Firefox (Private Browsing)
- Signed out
- Capture: full desktop screenshot