I think that you need to have the deathfish/life fruit in your sim's personal inventory, not the fridge. I'm sure that's how I've always gotten the ambrosia recipe to work for me.
I also believe that it is 'Have breakfast/brunch/lunch/dinner', as Ambrosia doesn't allow you to make group servings of it, only a single serving.
If having the ingredients in your sim's personal inventory doesn't work, maybe try to catch deathfish/grow life fruit yourself. There should be mods to enable you to raise the two skills to the required levels.