There are occasions when an approved food item, such as hummus, Greek yogurt, or bananas, may show up on your food list, and other times when it is not an option. Not all food items match the macronutrient allotment for each meal or snack. If a serving of the food has more fat, protein, or carb than is allowed, then that item will not be listed as an option.
Some foods are also added/removed to your food lists based on the glycemic index of the food and what nutrition cycle and phase you are currently on. If you are not finding the food you expected to see, double-check using the "search" feature in your food list - sometimes the item may just be in a different category than you expected.