Edit nutrition facts

Have you gone to Settings > Diary settings and pulled down to choose Fiber. I would assume that any food you logged in the past would then show Fiber. Just thinking out loud.

Maybe you can send a pm to CyberTone. He seems to be the resident geek on the forum.
http://www.myfitnesspal.com/user/CyberTone/profile/CyberTone?target=&redirected=true

​From your previous thread, community.myfitnesspal.com/en/discussion/10224950/macros, where you asked if you just need to log the protein from an egg, but not the carbohydrates, I am guessing you are using the Premium feature to Quick Add Calories + macronutrients (carbohydrates, fats, and proteins). If that is the case, you can not use the Quick Add Calories + macronutrients feature to log micronutrients, such as fiber, sugars, cholesterol, sodium, etc. You should not use the Quick Add feature to log all of your food. You should be either using the barcode scanner, or a text search, to locate the closest match that is already a shared food item in the Food Database that has the correct macronutrients and micronutrients. Only use the Quick Add feature if you can not find a match in the Food Database.

If I am mistaken, and you were creating a My Foods item, you could go to the My Foods area and edit the personal My Foods item to add the micronutrients.

Please see these articles, and many other helpful articles, on the MFP Help pages...
myfitnesspal.desk.com/customer/portal/articles/80938-how-do-i-add-a-food-to-my-food-diary-
myfitnesspal.desk.com/customer/portal/articles/838023-how-do-i-add-an-item-to-%22my-foods-%22
myfitnesspal.desk.com/customer/portal/articles/1027117-how-do-i-edit-or-delete-a-food-i-created-in-%22my-foods-%22