Why are there missing books in Protestant Bibles?

My wife and Ii, were recently in a Bible study with a group of Lutherans and found that although one of there foundations is Sola Scriptura, that they don’t have all the books in their Bible. What is the reason for missing books in Protestant Bibles and how should I bring up the fullness of truth with them?

These links should be helpful for explaining the Church’s continued inclusion of the Deuterocanonical books (sometimes referred to by Protestants as the Apocrypha, which BTW can also be found in the actual 1611 edition KJB which are still available.) in the Bible. If you have any further questions or concerns that are not answered by these links, please contact Catholic Answers directly.
Recommended Reading:

]The Old Testament Canon
]How to prove deuterocanonical books are inspired?
Did Catholics add books to the Bible?
]* Original books of Bible**

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