There are 2 things that I would check:
- You might be looking at a specific store only. If you're using the iPhone,
tap the shopping screen title (top center of the screen) to show the list of stores,
and tap All Stores/All Items. If you're using the iPad, tap the All Stores/All Items on the left.
- Check the settings of the ingredients that are missing. From the meal plan screen,
tap a recipe which has some of the ingredients not showing up in the shopping list.
Then, tap the pencil icon to edit the recipe, then tap Ingredients and tap an ingredient
that is missing. You'll find a switch labelled "Show In Groceries". Make sure that switch
is On if you want the ingredient to show up in the shopping list.