Speaking from a PVE-only point of view…
Can't Join Fractal in Progress
Same here, it has happened many times.
I’ve seem to encoutered a similar problem, yet different.
There’ve been multiple times I couldn’t join a fractals already in progress, but without any error notifications.
When my team is already inside, I get the pop-up message from the dungeon on my screen, but not with the preselected level.
Instead, I’m able to choose my own level – so not the one my team has chosen, yet – and not able to enter the instance. Even if I select the level my team is in, I just get a separate instance.
Relogging, closing the client, tp’ing, re-entering the map. All of the latter don’t seem to work. I always get the pop-up, but not the one where I can insta-join.
Quite annoying, since everytime I want to do fractals, I need to be the one opening, so I can’t join pre-existing teams.