Well, fist of all you may open a new thread for such questions, or use the contact form below the forum
On a second line, just because you have been Mentor Group member in the past then it does not mean that you continue to have access to Mentor Gorup Gold facilities.
Finally, when looking at your account you should be able to PM unless you got into our spam filter for some reason.
It may also be that the user you try to PM has disabled this function or is banned.