By default, podcasts hosted on Riverside are published to Apple Podcasts as audio-only episodes.
To publish video episodes to Apple Podcasts, enable video episodes and complete Apple's setup process. After setup is complete, every episode you create from that point on publishes to Apple Podcasts with video.
Only episodes you create after enabling video episodes will include video. Episodes created before that, even if scheduled to publish later, do not. Previously published episodes will not have video added to them.
If your previous hosting provider published video to Apple Podcasts, those episodes only keep their video while your previous hosting provider keeps the video files. If the files are removed, the episodes become audio-only.