The assets show up in my content manager just as they should, so at least it doesn't seem to be an issue with them. Let's see if there's a mod messing with things for you. Add the launch option -disableMods to Steam (right-click on the game, select Properties and add it in the box at the bottom of the window). Then start the game and see if they show up as they should.
Could you also check the Steam Workshop section of the content manager? With Steam connection issues they may show up there, while not in the Asset category, so checking both places will help us figure out where the issue is.