The Mod Manager does only show installed components. This way I am only able to uninstall stuff while i can't install any new files. Downgrading to build 798 solves the problem.
That's because by default, "components" are unchecked for some reason on the Mod Manager. I had the same problem, but I just put a check next to "components" and they all appeared.
check your default data path on the mod manager be sure that it point at the "good" package folder of the new build 841.