None - Re-save content or use playlists until issue is resolved.
If you are having either of these issues please can you post below:
1. Spotify version
2. Operating System (Windows/Mac/Linux/iOS/Android etc.)
3. Exact device you are using.
4. How many songs you have saved in Your Music. Easiest way it to press Ctrl/Cmd+a to highlight all items in Songs in the desktop client then attempt to drag them. You will get a small pop up detailing how many items are selected. Please ensure you have the "Hide Unplayable Tracks" option turned Off in Edit/Spotify > Preferences > Playback before doing this.