The teaching of the Church Fathers is that the Hebrew feasts are null and void because they were a prelude to the coming of the Messiah, since the Messiah is come, there is no reason for them. There was a short period between the Resurrection and the Sacking of Judea where it was permissible for Christians to take part, but after Titus came and punished Judea for the Crucifixion, the Synagogue was officially cast off and superseded by the Church. A Christian now taking part in a re-enactment of the Hebrew feasts (which there is quite some debate to be had if the modern erstatz jews and their customs are even remotely similar to what the Ancient Hebrews took part in) is basically denying Christ is the Messiah.