If the option is there, but greyed out, then the rubies are probably installed correctly. Make sure that the timber is a component at the top level of the model - not part of any other group or component. And the joint must be a sub-component of the timber component. Also, it's possible that you have already created a joint from it. When you right click on it, does TF ID: indicate that it's a joint?
If you're still having problems, you can email me the skippy. CB.