It's possible that your nutrition requirements are too strict to get much food variety. Your food filters could also be too strict for the number of recipes we currently have (we have a little over 3000 curated recipes as of March 1st, 2018).
Here are some suggestions for improving variety:
1. Tweak the Meal Type settings. Click the name of the meal in your plan, then the top "Edit" option. Increasing the allowed complexity and cook/prep time in a meal will vastly improve variety.
2. When regenerating the week, select the generator focus as "variety". This comes at the expense of grocery efficiency and macro accuracy, so you'll have to decide if the trade off is worthwhile.
3. If it's the meal or food refresh buttons that aren't giving you much variety, it could be because the generator is looking for a pairing of foods nutritionally similar to the previous meal and there aren't many available combinations. Try mixing up the other meals a little and coming back to the original one.
4. Make your food preferences less strict. Unless you're trying to go strict vegan or paleo, try selecting the "anything" diet type, and then only exclude foods you definitely can't have, or don't know how to substitute. Then if recipes come up with an ingredient that you don't like, see if you can make a diet-appropriate substitute that has similar nutrition (e.g. butter -> olive oil, wheat bread -> potato bread for gluten-free).