I also am having the same problem. I took the IP quiz and passed, and can upload mesh into sl, but cannot press the "Mesh" or "partial Mesh" options on marketplace. I would also like to know what to do.
I have a registered account, and have taken the IP quiz. I can upload mesh (.ddae) files into game. But when trying to set the items up on marketplace, it will not let me check "Mesh", or "Partial Mesh" options. Why?