A bookmark is not a video file
My List stores selections, and a checkpoint stores a season and episode number. Neither downloads the film or programme. This site does not provide a movie-file or series-download endpoint.
Check the selected service
If offline viewing is available, confirm the account, device, region and expiry conditions in that service’s app. Some editions or devices may not support it.
Before travelling
Finish the download on a reliable connection and test it inside the app. Check subtitles and audio language before leaving. A poster visible in a list is not proof that the full video is stored on the device.