You are viewing an Artist.
The Radio button under the Play Button will sometimes be grayed out.
If you go to the … menu next to the radio button it has an option for Radio which always works.
So I think this is what is happening…
The radio feature will mix that artist with similar artists but when it does not have enough data to make this playlist it is not available on the button under the play button but the button under the context menu will default to shuffling the artist instead.
So it is either a bug or an oversight that these buttons that are supposed to perform the same function are behaving differently.
