On my Ps4 it says at Spotify that I have to download Spotify then I go to the store and there it says that it is already installed. When I go to start there's a message that it could not be found and I'm back in the store start screen. When I go to the library under Spotify the bar is like when it is installed (completely full). I can't delete it there either.
Try uninstalling it again or restarting your ps4