You won't be able to apply a Thumbs Up to an individual artist. However, you should be able to use your 👍👎 for songs when listening from a station.
Looks like you've enabled a few complimentary sessions of Premium Access.
Does this happen when you're in the free session of Premium?
In the meantime, could you send over a screenshot of what you're experiencing?
To take a screenshot on your Android device, press the Home button and the Power button (on the right side of your phone) at the same time. You may hear a camera shutter sound (if your volume is turned on), and your screen will be captured.
To access your screenshots, go to the Gallery and look in the Screenshots folder. Send this photo as an attachment to your response.