As a Protestant of the Reformed persuasion, I must make it clear that the books of Maccabees are not considered to be inspired, Holy Scripture. This article explains why:
The book of 2 Maccabees consists of a Greek synopsis of a five-volume history of the Maccabean Revolt written by Jason of Cyrene. . . . The Second Book of Maccabees was written in Koine Greek, most likely around 100 BC. This work coheres with 1 Maccabees, but it is written as a theological interpretation of the Maccabean Revolt. In addition to outlining the historical events, 2 Maccabees discusses several doctrinal issues, including prayers and sacrifices for the dead, intercession of the saints, and resurrection on Judgment Day. The Catholic Church has based the doctrines of purgatory and masses for the dead on this work.
On the other hand, an important tenet of the Protestant Reformation (1517) was that scriptural translations should be derived from the original Hebrew and Aramaic texts for the Old Testament and Greek for the New Testament, rather than upon the Septuagint and Jerome’s Vulgate. Statements were included in the Protestant Bibles indicating that the Apocrypha was not to be placed on the same level as the other documents.
Protestants reject the Catholic doctrine of purgatory as summed up here:
According to the Catholic Encyclopedia, Purgatory is “a place or condition of temporal punishment for those who, departing this life in God’s grace, are not entirely free from venial faults, or have not fully paid the satisfaction due to their transgressions.” To summarize, in Catholic theology Purgatory is a place that a Christian’s soul goes to after death to be cleansed of the sins that had not been fully satisfied during life.
From this article Protestants reject these views of the Catholic Church:
Temporal Punishment: “purification of the unhealthy attachment to creatures, which is a consequence of sin that perdures even after death. We must be purified either during our earthly life through prayer and a conversion which comes from fervent charity, or after death in purgatory.”
Purgatory: “a state of final purification after death and before entrance into heaven for those who died in God’s friendship, but were only imperfectly purified; a final cleansing of human imperfection before one is able to enter the joy of heaven.”
The Roman Catholic Church teaches that the combined merit of Christ, the saints, and godly believers is stored in a place referred to as the Treasury of Merit (it is also sometimes called the Treasury of Satisfaction, the Church’s Treasury, or the Thesaurus Ecclesiae). And through apostolic succession from Peter, it is the Roman Catholic Church alone that has the authority to withdraw merit from this treasury and dispense it to believers in this life or in Purgatory to atone for some or all of their venial sin. This it does through the granting of Catholic indulgences. https://www.gotquestions.org/treasury-of-merit.html
The Reformed Protestant view of salvation, based on the Holy Bible, can be summed up thus:
I have been saved – in the past – from the penalty of sin – by a crucified Saviour: “For in this hope we were saved" (Romans 8:24). “For it is by grace you have been saved, through faith – and this not from yourselves, it is the gift of God” (Romans 2:8).
I am being saved – in the present – from the power of sin – by a living Saviour: "For the message of the cross is foolishness to those who are perishing, but to us who are being saved it is the power of God" (1 Corinthians 1:18).
I shall be saved – in the future – from the presence of sin – by a coming Saviour: "Since we have now been justified by his blood, how much more shall we be saved from God's wrath through him!" (Romans 5:9)
Protestant Christians acknowledge only Christ Jesus as the head of the Church, and as He alone is our High Priest forever (in the order of Melchizedek), no mortal man can grant or withhold salvation or somehow pay to have our mortal sins forgiven either before or after death.
Jesus, though God from eternity, became a man in order to suffer death and serve as our High Priest (Hebrews 2:9). As a man, He was subject to all the weaknesses and temptations that we are, so that He could personally relate to us in our struggles (Hebrews 4:15). Jesus is greater than any other priest, so He is called our “Great High Priest” in Hebrews 4:14, and that gives us the boldness to come “unto the throne of grace, that we may obtain mercy, and find grace to help in time of need” (Hebrews 4:16 KJV).
You ask how is 2 Maccabees 12: 42-44 interpreted by denominations not accepting the existence of purgatory.
The answer is straightforward. 2 Maccabees is not regarded as the Holy and Inspired Word of God and is rejected. The Bible says that man is destined to die once, and after that, to face judgment (Hebrews 9:27). Reformed Protestants respond by saying there is no intermediate state called purgatory.