Three different things can be saved
Save title keeps a film or series reference in NetFilm's local watchlist. Create backup produces text containing supported list entries and checkpoints. A video download is different: it stores playable media through a viewing service that supports offline access. The first two tools do not perform the third task.
Prepare the viewing app before leaving
If the service offers downloads for your device and edition, select the required films or episodes there. Verify the season and the language tracks while you still have a connection. Open the download area and check that the items completed rather than assuming a tapped button means everything is ready. A long series is particularly easy to prepare incorrectly if only the first few episodes were selected.
Know what does not transfer
A NetFilm list backup does not contain movie files, subscriptions or another app's credentials. Downloaded media may remain inside the service that supplied it and may be subject to expiry or renewal conditions. Confirm those details in that service before a trip. Changing browsers does not move offline video, and installing a home-screen shortcut does not create offline playback.
Use Watchlist to plan what you want, then use the selected viewing service to prepare its supported downloads. If your immediate problem is a missing list rather than a missing video, the backup guide is the relevant next step.