If you can not see your custom items when searching it is usually one of the below issues:
You have not added permission for the user or assessment to use that food. You can learn more about permissions here https://help.foodzone.io/en/articles/3179880-custom-foods-and-recipe-permission
Your custom foods where added to a different database than the one the user or assessment is using. Foodzone has many advanced food databases versus a normal calorie counter. The databases do not share nutrients and foods as they are usually for specific parts of the world. You can learn more about choosing a database here https://help.foodzone.io/en/articles/3111258-choosing-a-food-database
You have multiple foodzone accounts and have logged in to the wrong one.