Make a complete offline test
Select the film in its viewing application, finish any supported download and confirm it opens without a connection. Check the spoken language and subtitles at the same time. A completed poster page in My List does not perform this test.
Why people mention SPlayer
Some OnStream app users describe a separate-player handoff. The website here uses JustWatch for viewing choices instead. There is no hidden SPlayer installation or transferable download queue attached to the saved-title button.
When the button is greyed out
Check that application’s title and device rules. A download can be unavailable even while online viewing works. Keep an alternative film ready before travelling, rather than discovering the restriction after your connection disappears.
Space and expiry
Use the viewing app’s own download screen to inspect completed files, storage and expiry information. Do not delete another person’s downloads to make space. Choose a shorter or smaller supported option if that better fits the device you are taking.