Hebrew 9: 24-28
For Christ has entered, not into a sanctuary made with hands, a copy of the true one, but into heaven itself, now to appear in the presence of God on our behalf. 25 Nor was it to offer himself repeatedly, as the high priest enters the Holy Place yearly with blood not his own; 26 for then he would have had to suffer repeatedly since the foundation of the world. But as it is, he has appeared once for all at the end of the age to put away sin by the sacrifice of himself. 27 And just as it is appointed for men to die once, and after that comes judgment, 28 so Christ, having been offered once to bear the sins of many, will appear a second time, not to deal with sin but to save those who are eagerly waiting for him.
Luther assumes that the Mass and Calvary are two different sacrifices that there was this one sacrifice on Calvary and that the mass is another sacrifice that somehow has to add to the sacrifice of Calvary but what Trent and the catechism of the Catholic church respond to that error by saying is no you misunderstand it there's only one sacrifice and that's the sacrifice of Jesus Christ but that one sacrifice of Christ on Calvary is made present in a different mode in the unbloody sacrifice of the Mass, so Calvary is a bloody sacrifice and the Mass is an unbloody sacrifice but the sacrifice of the Eucharist and the sacrifices of the cross are one single sacrifice
Luther couldn't see how the Mass could be a sacrifice is because he focused on Calvary and forgot about the Ascension
If you try to understand the Paschal mystery and you think it just has to deal with Jesus' death and you forget about His Resurrection and Ascension you're going to miss the boat because what the Mystery of Ascension does is it reveals how Jesus takes the earthly sacrifice of Calvary into eternity and once you understand that he takes that earthly sacrifice into eternity you can understand how now from heaven he can be made present his Body, Blood his Soul and his Divinity on every altar throughout the world every day until the end of the ages, until the end of time.
Jesus fulfil the feast of Yom Kippur and He inaugurates the new day of atonement that takes place not on time but in eternity.
Summary:
The key is the the Mystery of Ascension, it reveals how Jesus takes the earthly sacrifice of Calvary into eternity, you can now understand how from heaven He can be made present His Body, Blood, Souls and Divinity on every Altar throughout the world until the end of the time.
