You are trying to nest the runtimes which will lead to confusions.  Understand, each linked folder must contain only one runtime folder.  If your Poser content already contains a runtime folder then the Sofia folder cannot be placed into it.  You can take the Sofia runtime and merge it with the Poser Content runtime, but you cannot do what you described.

Open your Sofia folder and verify that it has a runtime folder.  Then open that runtime folder.  Please describe what is in that folder.