I invite someone to join my empty lobby like as if i invite someone to me be4 i play online or zombies and they say it says lobby not joinable. Same when they invite me it will tell me lobby not joinable??? Have no idea why!!!!!!!!?

I Will invite someone to join my empty lobby be4 we play online or zombies and it will tel them lobby not joinable. And aame when someone invites me it will tell me lobby not joinable when it is not full and not even in game. Where like when u invite a friend to play zombies and when u try to join it will say not joinable??????