as the title says, to reveal the Treasure Wraith you need to damage or attack the chest it is in. I’ve done that on two different occasions and the rare did not emerge.
I haven’t seen this fail to spawn the rare, but it sometimes takes a bit of damage. On Fury warrior, the only real option without spending cooldowns is spamming Whirlwind, and it takes about 10 seconds of doing that.
Alternatively, you can still right-click the chest to make it appear if it’s giving you issues, and just accept the gamble that it might stun you instead of getting stunned when it appears.