The phrase "full fellowship" refers to a close and supportive relationship between people who share common beliefs, values, and goals. It means being fully included and accepted within a group or community. Full definition
So I have prepared this Bible message to show what is a backslider, why people backslide, the sorrows and punishment of backsliding, to show that the true backslider is really saved, and to show how any Christian who has fallen into sin can get back into full fellowship with God and have the joy of his salvation restored. (religion.blogs.cnn.com)
Philip told the eunuch about Jesus, convinced him that Jesus was the fulfillment of the very scripture he was reading, and that no handicap, physical or otherwise, would exclude a person from full fellowship in Christian faith. (religion-online.org)