I was trying to get in Caudecus’s Manor. We had five people in our party. The pop-up thingy didn’t work, it just disappeared after I clicked join. I was able to get in and so were a few others from the party but we were all in different instances. After we left to try and re-enter it wouldn’t let us in at all. We had to restart the client to get back in the dungeon but then had the same issues of not being able to get in the same instance. Hope this helps! Rather annoying.