I have the same issue. I tried joining the dungeon with a group on the 26th but I found myself alone. So I walked out and tried to get back in and couldn’t. Another group member had the same problem while three others we’re able to enter and exit repeatedly. Even ungrouped I couldn’t enter the dungeon anymore until the next day. On the 27th I entered alone, walked out and couldn’t get in anymore.
I’ve submitted a bug report aswell. Hope this gets fixed soon.