Stuck after selecting mission.

Having this same problem. I just kept retrying and eventually it worked, but it's annoying. Sometimes it even crashes the game.

go on esc and set to back satrt point

and keep tring

Best thing to do if you do not mind is Auto-forming parties instead of Solo- which seems to be the primary issue _{(Due to server congestion)} that a lot of players are running into.

I've personally found that i havn't had issues using the auto-formation feature and loading into Dungeons that way instead.

I have the same problem with the missions as well as the end of the tutorial.