Diagnose: uploaded subtitle file is not showing
Dynamic diagnostic state for this problem. Choose a file to run the diagnostic tree; the page rerenders with ranked causes and recommended fixes.
Direct answer
Subtitle files can be silently rejected when the format is invalid, the language code is wrong, or the destination has no caption track enabled for the surface. Validate the file with Caption QA before uploading; double-check that the destination has CC turned on for that surface.
Run the diagnostic tree
The tree combines this problem's static cause ranking with the values the diagnostic engine reads from your file.