What you were expecting to happen, and what actually happened?
Opponent’s Poison Master to blow up only Green Gems (there was only 1 on the board)
What are the steps to make it happen again?
Run into Poison Master, turn Green gems into another colour (with Alchemist or Valkyrie, for example)
Do you have any screenshots or video you want to share with us so we can see the problem? Attach them to your post!