Why does 7 day epc not show for some advertisers on cj?

I noticed that some advertisers do not show a 7 day epc for some of their links. They all show 3 month epc and some show the 7 day epc for the same link as N/A. It just so happens that the ones that show N/A are the ones I am promoting and I have mysteriously not had any sales in the last week even though before I convert 1 in 44 typically. Could it be they have not updated or something and that's why my sales and the epc for everyone is not showing?