It sounds like the full-screen option is disabled by the platform hosting the Databricks training videos. If that's the case, it may be out of your control. However, you could try these workarounds:

1. Browser Zoom: Use the zoom feature (Ctrl + "+" on Windows or Cmd + "+" on Mac) to enlarge the video area.
2. Inspect Element: Right-click the video, choose "Inspect," and check if there's any way to manipulate the frame size.
3. Different Browser: Sometimes switching browsers like Chrome, Firefox, or Edge can make a difference.