Have you noticed songs from your Spotify/Deezer playlist suddenly grayed out when you have listened to them for ages? Here is why:
Removed by artist
It is possible a song has been removed by the artist if are no longer wish to be online or require a repair to the song like artwork, title etc…
It also could be that the artist no longer wanted a song on another platform.
Could be removed due to copyright or take down request by another party or artist.
Restriction could be set by labels and artists whom do not wish to have their songs released elsewhere or releasing only in certain regions due to licensing deal or even copyright.
If you’ve enabled show hidden songs on both Spotify and Deezer, you will able to see them, but unplayable.
Unless you never connected to the Internet, downloaded (offline) music from both Deezer and Spotify will be removed or changed once the Internet connection is established.
Apple Music may remove the link entirely or may asks you to change the region. If you do end up changing the region, it may not always work and your default payment will be changed or removed. Songs purchased before removal is unaffected.
If a song is unavailable on beatport due to country restrictions, it will say something along the lines of restricted in your territory. Removed songs will simply get redirected to homepage just like Apple Music.
If you uploaded a custom song on Deezer (which has been removed) with the same title and artist prior to removal and the song is reinstated later on, the song from the playlist will be swapped to the official release (you may have to delete from custom MP3 section).
Other places may just remove the link entirely.
Soundcloud may have a copy of the song. But usually is illegal to upload a song users don’t own or have the rights to.