My brother and I had just gotten to the ancient door in “descent into torment”, used the key to open the door, and before we were able to go through it the door closed and locked. To make matters worse, we cannot open the door again this session. After going through 3 levels of a dungeon, fighting a hard boss, and using up a finite key (which can be crafted, but is expensive), not being able to get the reward of going through the door feels like a colossal troll on the game developers part. We are not happy.
You have a few seconds to enter and a text telling you to hurry. Not sure how you managed to not enter in time, but it is the kind of thing that happens at most once 