Did you checked that you where in the Offline mode?
I had this problem during the beta, and i didn't checked that i was in offline. It seem to change, but was purely cosmetic during the online campain.
Please accept my apologies as I don't know much about the game, but I looked into your case anyways. It looks like you experience a normal phenomenon.
In the Expedition i kill Monsters to get to the Boss.....After killing the Boss there is a Loot Box.... when i loot the Box Then there is Victory Animation with a summary and i get back to the Dungeon..... i can Loot the Box and there is a Portal to stormfall. But Not an other Lvl. I Made a lot expeditions But its everytime the Same.
Can someone help me?