Missing songs from artist

[c-a-t-e]

So I recently noticed some songs are missing from my playlist ( not local songs ), these songs are specifically from the artist "Hyakkei", I searched them again and the artist appeared  but no songs appear in the overview, I couldn't even access the radio as only an error comes up. Then I searched on my PC and thus the same result. I even tried my friend's PC and nothing shows up in the artist's page

Is this an issue on my end or something else?