I know that this probably isn't the solution but since I had similar things happen to me, I'll just bring it up.

Sometimes when I install content, I forget to change to the library that the content is actually in, so initially I think that the content didn't install.  For example, I'll install a figure and forget that I'm actually in the Pose Library looking for a figure.  The figure didn't show up because I was in the wrong library.

I have also had a similar case when installing hair.  I expect to find it in the hair library, but when there's nothing there when I go to the hair library.  After that I end up checking the figure library or the prop library in order to locate the hair.

It's a long shot solution for you but it happens.