No option to sync the CC text for pop-up

You could always add a text caption to the popup group that simulates CC, as long as the text fits completely inside the caption.

As Rod points out, the CC text which is synchronized with the audio needs the functionality of the timeline. At this moment the only audio type that is linked to the timeline is slide audio. It is possible to synch with text captions if object audio is fixed on the timeline, but not if you use it to be triggered by an event like is the case for a popup: in most instances the play head will be paused at that moment.

CC text is part of the Captivate skin and will only sync with the audio applied to the slide timeline, not the Object Audio that is added to objects such as buttons, captions etc that appear on the timeline.

Captivate does not provide a default solution for synching CC text with Object Audio.