This question is occasionally asked by developers who've configured the latest release of THEOplayer.
The most common reason on an older build why closed captions are no longer working is because the
texttrackrendering feature isn't enabled. To verify whether this feature is enabled you can execute the query below.
var subsEnabled = THEOplayer.features.indexOf("texttrackrendering") > -1
Starting in THEOplayer version 2.80 the
texttrackrendering feature is no longer an optional feature. It is instead part of the default build, and is always enabled.