Hello and welcome to the community!
I could reproduce your issue on my iPhone 5 and will see if i can get some more information about it. Are you using iOS 8.1? Have you tried a clean reinstallation (You will lose and you have to sync your offline playlists again)?
Hi.
I had a similar probelm here, but a re-install didn't work.
If go online temporarily and then back offline, can you play the album you were trying to play?
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