While the install process of ZC 1.5.5 addresses/corrects the dropdown condition (removal of the infamous three values that were previously stored in gID=0 (and potentially erased by incorrectly formatted SQL statements) but have been moved to gID=6).

The instruction at the following link ought to resolve the issue with the dropdown. Instruction provided above to discover the current value for Grid (seeing as Grid was previously in existence within the store) ought to resolve the display of grid related attributes, although the code ought to have picked up that characteristic upon initial attempt to display a product that had attributes assuming that the existing option name string was that of 'Grid' per the original install of this plugin.

If the SQL above becomes necessary, then in the case(s) where a value of 6 other than for gID are used in the existing store, then they should be substituted with what is discovered by inspection of the option name page's html source code.