Novenas have, unfortunately, become rare in some corners of the Catholic Church in America. Along with kneeling, confession and a host of other ancient Catholic practices novenas somehow seemed to have gone "out of fashion" in the post Vatican II Church.
Certainly moving the celebration of the Ascension from its traditional day of the Thursday forty days after Easter to the following Sunday has confused the issue.
What does the day that the Ascension is celebrated have to do with novenas?
Far from being a practice originating in the Medieval Church the concept of the novena is based on the nine days of prayer and meditation practiced by the Apostles in the time between Christ's Ascension into Heaven and the coming of the Holy Spirit on Pentecost, a period of nine days.
Pentecost itself was a day which pre-dates the founding of the Church associated with the Jewish festival of Shavuot which commemorates the deliverance of the Ten Commandments to Moses, which occurred fifty days after the Exodus, and so fifty days after the celebration of the Passover.
In the later Church the practice of the novena often centers on Mary and in this period of the Early Church Mary was indeed present with the Apostles in the upper room during this period, and on Pentecost itself.
So movement of the date of the celebration of the Ascension does obscure the significance of this nine-day period and this relationship to later practice.