I was playing the Battlegrounds, with the character Nefarian and twice in the Battleground, when I clicked the Hero Power, it didn’t work.
It showed that it activated.
However, when the combat battle began, the Hero Power didn’t activate.
I had the coin to buy the Hero power and I activated it when I had plenty of time before the battle begins.
It cost me the game because I was facing a Bubbled Murloc team with not too much health. The Hero power could’ve saved me.