Problems with conditional display of fields in food ingredients database

I have checked the synthax over and over but can't make this work...

I want to create categories and sub-categories but, in order not to crowd the input screen, to display the sub-category only when the correct category above is selected.

The main Category can be Seafood, Meat, Vegetable, Dairy or Dry Store. For each of those I have created an additional field e.g. Dairy Category (eggs, cream, milk etc.). I also create sub-sub categories as needed (e.g. seafood/shellfish/crustaceans/lobster).

So I am applying a conditional test to display a sub-category as needed. For example the Seafood sub-category (fish/shellfish) will only appear if the Seafood main category is selected. The logical test is: Category = "Seafood"

Well it's just not working. I've tried both visual and text editing, my sub-categories just won't appear.

Anything I should do? Is this approach of many sub-categories optimal? (versus, say, sub-tables which I don't really understand!)

Many thanks for any insight

François