As it says on the tin:
Rounds won't start in Murkwood Arena -- I am stuck on Round 0, and whenever I press the "start next round" button I just get the marching dots animation endlessly. Navigating away from the page doesn't complete the round, it just puts the button back.
However, if I refresh or navigate away from the page, I do get progress on the "Win Murkwood Arena Rounds" task.
Tested on Brave and iOS Safari, same behavior on both.