When using the Team Up feature, I've been finding that it doesn't work. When someone else joins my team and the counter reaches zero, either I go into the dungeon alone or nothing happens at all and it just goes back to "Waiting." Has this happened to anyone else?
If you have your volume on, you will hear a chime type noise if someone joins or vacates the team up before it starts. When you hear the chime, click on the icon (upper right of screen) to see the status of your team. I've noticed that there are 2 different chime sounds; one for a joiner, one for if someone leaves. Hope this helps.