Why is St. Alipius a saint?

There is no saint named Alipius. There is, however, Saint Alypius of Thagaste who was bishop of the see of Tagaste (in what is now Algeria) in 394. He is also credited with building the first monastery in Africa. He was a lifelong friend of Saint Augustine of Hippo and joined him in his conversion. Little is known about his life or the reason for his sainthood but he was added to the Roman martyrology in 1584 by Pope Gregory XIII.