(see attached screenshot)
Try to add captions file to uploaded file, after you have waited for 1-3 minutes to see anything on the screen (MH-10260) you can attach the caption file. Once caption files has been attached you can roll over "CC" icon to turn off or on. A user may be confused when they hover over the icon it glows and when they select it, or turn captions on, the icon is still glowing.
Solution: Create different states (Off, hover, on) to ensure state of icon is clear to end user.