One possible solution to this issue could be to ensure that the recorded videos have sufficient audio content. Live titles in Apple Clips often rely on audio cues to detect when to display the titles. If the audio in the recorded videos is too low or absent, it may prevent live titles from being added.
Additionally, you can try adjusting the volume levels in the recorded videos or adding background music or ambient noise to ensure that there is enough audio content for the live titles feature to work properly.
If the issue persists despite these steps, it may be helpful to reach out to Official Apple Support for further assistance. They may be able to provide specific troubleshooting steps or insights into why the live titles feature is not working as expected in your students' videos.