The label belongs to an edition
A film can have several viewing editions. One may include 4K, another Full HD, and another a different set of audio tracks. Look at the offer you are opening, not only the poster or the film’s release year.
More detail and a reliable connection
1080p commonly describes a Full HD picture, while consumer 4K commonly describes 3840 by 2160 pixels. The larger number is useful only when the available edition, device and connection support it. A stable lower setting can be the better choice on a small screen or busy network.
Let automatic quality settle
Where the player offers automatic quality, allow it time to adjust. Repeatedly switching to the highest option can undo that adjustment before you know whether it helped. Test with one scene, then change only the setting that addresses the problem you can see.
Do not mix picture and language problems
Raising the resolution will not add a missing subtitle track. An audio delay will not necessarily disappear after choosing 4K. Check video, sound and subtitles separately. The subtitle guide and playback help cover those other cases.