Pingbacks Aren't Showing Up

Hey everyone. I’m doing some article marketing and some other types of marketing for two different sites. I’m doing the exact same thing for both of them and one of my sites is getting like 10 pingbacks showing up in my comments everyday,and the other for some reason isn’t getting any pingbacks at all. i know it’s getting backlinks, but no pingbacks.

In the discussions settings I have pingbacks turned on and I have it turned on in my regular posts, but still nothing.

Does any one know what I should do?