Status: NOT JOINABLE, HELP!!!!!!!!!!!!!!

HI! im getting really tired of the legend in my profile that says Status: not joinable, I’m talking about when you click X and can see your whole friends list. Everyone in that list says Not Joinable. I want to know how to make myself joinable, as I’ve tried many times with friends trying to group up and it won’t work.

My NAT is open, i have changed mi privacy settings to open, i have good internet conecction, and i have played Halo since Halo 1 so please tell me how yo fix this, or is it that the servers for mexican players (im mexican)dont work???