Socket Problem

I just got my S3 Chest piece and socketed one red epic gem that does 20 attack power. Apparently, I should be able to socket another red gem along with a yellow gem. I purhased another reg epic gem that does 20 to attack power with honor points and tried to socket the gem to my chest piece. I was not able to socket the gem even though I have another avaiable space for another red gem on my chest piece. The error message I get is "You have the maximum number of those gems socket into equipped items." I'm confused why I'm getting this message when I have red epic gem that matches the available space on my chest piece for another red gem. Can any\one help and tell me why I'm getting this error message? Thanks!