I class changed from dh to monk. Changed legendary gems and had to make one dormant. I played monk for the day and then class changed back to dh. I went to armory activated my build and when doing so i lost gem power. Both gems i used in the power unpower process were both powerless.
Usually this is the case of reso or power gems being lost in awakened slots. The armory is terrible for moving and removing said gems which can cause the main gems to become dormant.