From the above image, you are running Revit 2014.
Autodesk Revamped the Lookup table methodology to remove the hard-path Lookup table references. Lookup Tables are now embedded within the RFA.
As mentioned above you can click manage to ensure that the lookup table is referenced in the family correctly.
There is a parameter "Lookup Table Name" that will need to contain the filename of the referenced lookup table without the ".CSV" extension.
All formulas for the lookup table are now managed using the size_lookup() function.
here is a youtube reference for the new functionality: http://www.youtube.com/watch?v=Uw7gcPAryaI