"Not yet encoded"

Hi. Googled, checked everywhere, no answer to be found, so I’m asking the community.

I went to play an album i’ve listened to once a day for the past 5 years, and suddenly one track is greyed out, listed as “not yet encoded.” checked Daughter’s other albums, and sure enough, random tracks from another album are also greyed out. 

Is there any way to listen to the full album again or are those songs gone for good? This is across the desktop website and android apps, so it’s not my laptop or phone doing this.

Thanks

Cos