I was playing the emperor's retreat dungeon solo and I ran out of mana. So I popped out, ran around to get mana, and came back 5 minutes later. My dungeon had been reset What happened I've done this before and never had an issue. Why now?
As far as I know all dungeons close within a certain amount of time. I have had dungeons close on me all the time. The new button that lets you transport back to the dungeon, I believe has a function if you hover over it with your curser it will tell you how much time you have to get back to your dungeon before it closes. It just happened that you were unlucky and probably missed it by a minute or two. If I am doing a dungeon solo I try to carry extra potions so I can use them and port back as fast as possible.