I've come across a bug on Windows. The radio button says pause when I never started it, it should say play.
Steps to replicate:
1. Start playing a song on the artists page.
2. Right click artist picture and click on 'Go to artist radio' on.
3 The button state says pause, but when clicked it starts the radio.
This only happens if you are playing a song from the same artist that you're trying to start the radio on.
We gave it a try on our end and noticed that this happens because the song that you initially chose to play is still playing and it might be included in the artist's radio.
Give us a shout if there's anything else we can help out with.