It says that it takes time for your site to get weight when you first sign up. They want a couple days to see your traffic.
How long did you wait? I waited a few weeks and mine is steadily going up. Plus, I have subdomains working in my favor adding to my weight. I'm not going to give up that easily.
Well, that's good you didn't give up all hope. Just keep testing, I'm sure it'll work out. Good Luck!
I have a site that has over 200K pages in the Coop. The first 4 days showed around 50 in weight then started to climb rapidly, sitting about 50K now.