I have added my local files with Spotify, but it won't sync them with the ones on the cloud. I know for sure that those albums exist on Spotify, because I still have access to them throught an old playlist, though I cannot play them. My problem is basically when I add an album, Spotify adds the "Artist and Album" but it won't sync it with it's cloud, therefore there isn't any album art nor can I click on "Go to Artist" through the added song.
On the first screenshot you can see that the added songs are playable but not officialy synchronised with the album, since there's no album art and the links to Artist and Album are unavailiable.
On the second screenshot you can see a playlist, which I've made many years ago, containing the band's album, but it is not playable through my now-added songs, although the song are the same and it was playable back in 2015.