ISB ~ 2 John 1 v9

one who goes ahead:The Greek text envisions someone who “goes beyond” the limits of authentic Christian doctrine. No hint is given as to their motives, but such individuals are often described as “progressives” who not only embrace novel teachings, but who leave behind the truths of apostolic faith in the process.

does not have God:Faith in God and fellowship with God go hand in hand. John is insistent on this point and warns that breaking away from the true faith means breaking away from the one true God.