Maybe a simple newbie question… bought Arc today and easily installed it to my LG OLEDs HDMI-ARC port (no eARC available).

Can get sound from TV and Spotify, but only in stereo. Tried several movies (from Disney+) today with Dolby Atmos mark, but getting still only stereo sound (checked that in the app).  Have been browsing my tv-menu and can see that Atmos is selected (but greyed out as only selectable when using tv’s own speakers). No selectable options available more (even how hard I scroll - saw other thread with this solution so wanted to note this…) 

So far tried: several re-start and cable re-instal of both arc and TV. Re-installed arc from app and re-connected it to tv again. Check that there are now updates available to tv, arc or any app in tv. 
 

Not yet tried optical cable connection.

Any good ideas or advices!