Hi, welcome to the community, and sorry to hear one of your favorite albums is no longer available. Unfortunately, this is up to the artists and labels rather than Spotify itself, meaning they probably requested the album be removed. Please see this FAQ page for more info.
The reason is that the artist or their music label has decided to remove it from Spotify.
The availability of songs on Spotify is up to the artist and their music label.
Spotify has no control over what content is available.
Sometimes it is only available in certain countries, while access is blocked to others.
Sometimes the album or song will be unavailable temporary, and come back again later.
You can find out more information here
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