In order for a video to be in the Resume section of the Watchlist where you can continue watching where you left off:
The video must be a full episode
You must have watched more than 5 minutes of the video.
If these requirements are not met, the video will not appear in the Resume section of the Watchlist. The video will, however, remain in the Saved and History sections of your Watchlist. From the Saved and History sections, a video must be played from the beginning. The video can only pick up where you left off if it is in the Resume section of the Watchlist.