I am so sad that Apollo Sunshine's 2005 EP "The other side of the world" is missing. The song Venice Beach on that album is by far the greatest thing the band has ever produced. I would be so happy if that song was added. For reals.
You can use this form to provide the Spotify team with feedback regarding music you would like to see added to the platform. When doing so, do please keep in mind that this is an internal list they will use at regular intervals, to see how much interest there is for any given band. Submitting a name in that form or this thread doesn't mean they will magically be showing up soon.
You can also reach out directly to the artist or record label to ask them why the music isn't on Spotify. I'd recommend using Instragram DM or a linkedin email for this!