You need to be sure that you're using the correct caps. If you try using caps with 12 digit codes, you'll get that message (and each time you get that message, one of your daily "attempts" is used, out of the five you get each day), same as if you try it with any other "wrong" caps.
The safest way is to stick with red caps with 14 digit codes, or the Arctic Home caps with the 14 digit codes. If you don't have caps, then use flaps, but they *must* be Coca-Cola products (actual Coke, now), and again: 14 digit codes.