Just to clarify a few things, are you writing you are having issues with playing content from this artist, even content by this artist available to you?
I just went through a few of the releases listed for me, and checked for region availability for the releases by this artist, and the listening regions vary depending on the release of which users from which listening regions have access to certain releases by this artist.
Are you and your friend from the same listening region on the Spotify service? Meaning you both set up your Spotify accounts from the same Country?
Can you list which Spotify apps and their versions your are having this issue with, what about the webplayer can you play the same artist content there? https://play.spotify.com/
Have you tried logging out the Spotify apps on your devices, and then do a device reboot, and log back into the Spotify apps again and see if you can play the content now?
Can you list your listening region you set your Spotify account up in? Or you can go to this third party lookup service below, and double check which content by this artist is currently available to you? https://jcheng31.github.io/isitonspotify/