Turn off closed captioning

• You can turn off the default setting for closed captioning in Settings﹥Accessibility﹥Subtitles and Captioning﹥Closed Captions and SDH﹥Off|On.
• You can turn on Automatic Subtitles in Settings﹥Video and Audio﹥Automatic Subtitles﹥On|Off (based on a mismatch between the audio language and the device system language).
• You can turn off default subtitles in Settings﹥Video and Audio﹥Subtitle Language﹥Off.
• You can change the current Subtitle to Off to disable Closed Captions for the currently playing video, as with any other subtitle. Change subtitles or languages for videos in the Apple TV app or iTunes Store - Apple Support

Verify that the Accessibility Shortcut isn’t being used accidentally (triple-click Back/Menu). You can disable or edit the Accessibility Shortcut if needed. Accessibility shortcut configuration on Apple TV - Apple Support