@Vertesept One thing to note is that if you're using your thumbs on these stations, certain modes will disappear for 24 hours if an excessive amount of thumbs down ratings are given.
This being said, I do see you are upgraded to Pandora Premium.
Rather than listening to Artist Only Mode, another option would be to navigate to an Artists page, and then playing their Top Songs:
If you press play on any of these tracks, you can then highlight the shuffle option to cycle through all of the songs by this artist.
Hope this helps!
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