(iPhone 8, Samsung Galaxy 9, Macbook Pro late 2016)
(iOS 10, Android Oreo, Windows 10,etc.)
A lot of users have had an issue with Shazam not uploading new songs to the Shazam playlist on Spotify. According to Spotify help, the way to fix this is to delete the Shazam playlist, disconnect spotify, then reconnect it.
From that point forward, only newly Shazamed songs appear on that playlist.
Spotify has responded to this by saying "this is why we recommend that you don't delete your playlist".
This is an issue for a lot of people, I'm quite surprised we are being fobbed off