It appears that Ratramnus’ view of the eucharistic body and blood of the Lord was symbolical, i.e., the body and blood of Jesus is not in truth in the eucharist but only in sign or figure. At least his theology lends itself to this interpretation and it was a symbolic interpretation of the eucharist attributed to him that prevailed among later controversies concerning the real presence of Christ in the eucharist and subsequent theologians. That the eucharistic bread and wine is only symbolical of the body and blood of the Lord and not in very truth substantially changed into the body and blood of Jesus has been condemned as heretical by the Church. Certain parts of Ratramnus’ work were condemned as heretical at a synod of the pope and bishops in Vercelli around 1050 at the time of the controversy surrounding Berengarious who was influenced by the symbolism of Ratramnus. Berengarious also held that no real change takes place in the nature or reality of the bread and wine at the consecration but that the bread remains bread and the wine remains wine after the consecration as before the consecration which is contrary to the Church’s doctrine of transubstantiation which at this time was being more precisely defined as the true doctrine, faith, and Tradition of the Church in answer to various eucharistic controversies.
The teaching of Paschasius Radbertus, on the other hand, in accord with the patristic tradition and faith of the Church, was that by the consecration of the bread and wine at the Mass, the body born of the Virgin, suffered and died on the cross, and rose from the dead, and the blood that Christ shed on the cross, are in all truth, truly present in the consecrated bread and wine. The eucharistic bread and wine ‘must be believed to be none other than the flesh and blood of Christ.’ Radbertus’ teaching is substantially the faith of the Church with various difficulties and more precise terminology to be ironed out in subsequent centuries especially among the scholastic theologians and most notably St Thomas Aquinas.
Reference: The Hidden Manna - A Theology of the Eucharist, by Rev. James T. O’Connor (2005). This is an excellent book. I highly recommend it.