If your Factor coupon is not working, it's normally due to one of these three reasons:
Misspellings: make sure you have copied or typed your code properly.
Expiration date: Factor 75 coupon codes are normally available during a specific period of time. If you copied it yesterday and try to redeem it today, maybe it is too late. If that's the case, don't worry, check again the promo codes posted at Coupons4Real and look for another one.
Coupon terms and conditions: Some coupons are only valid for certain products. Double check that the code is applicable to the meal plan you're trying to achieve.