Mobile user here, not sure if that changes anything, but after defeating the Illidian Encounter in the MotLK Prologue, I went to bed so I swiped the app away. When I logged back on the next evening the rewards chest is unable to be opened even after defeating Illidian again. Probably my own fault for not going on to the rewards page the first time but figured I would report it anyways. Thanks.
I encountered this just a few minutes ago. But for me, I finished the run and the chest opened itself and I was given one card pack. Not sure what the issue is here unfortunately