If your camera is only taking pictures for the video interview, that indicates that you have not given permission for the webpage to use camera/microphone.
Once you open the link, the site will ask about permissions to use the camera and the microphone. Choose 'Allow'.
You can check that you have allowed the site to access both the camera and the microphone from the address bar:
Chrome:
Click the Settings-icon (as showed below).
Make sure to add permissions to camera and microphone.
Remember to refresh the page after giving the permissions (the page will give an option to 'Reload'.
Try recording again.
Firefox:
Click the settings buttn next to the address bar
Click "Blocked Temporarily"- button in microphone and camera
Refresh the page
Try to record again
