What you were expecting to happen, and what actually happened?
The enemy troop should be burned. Because it’s written that an enraged attack ignores traits.
What are the steps to make it happen again?
Enrage the 1st troop which has Aflame trait and then match some skulls.
Do you have any screenshots or video you want to share with us so we can see the problem? Attach them to your post!
Just before matching the skull (the 1st troop is Goblin Rocket):
Just after matching the skull: as one can see, the Golem is not bunred.