Add olive oil to Instant Pot and set to sauté mode. Add onions and garlic and cook until soft. Add meatballs and slightly brown. Add carrots, Greek seasoning, orzo, and broth. Hit cancel button and set to manual for 10 minutes. Do a quick release. Add spinach, red pepper flakes, cheese, and lemon juice. Stir until well combined. Top with fresh chopped parsley and extra Parmesan before serving.