It has the NT, minus some missing pieces. It also contained the Revelation of Peter, a Gnostic text.
If the church in Rome then possessed infallibility, a Gnostic text would not have been within their canon
(1) I don't see where I brought up the Muratorian Fragment in this conversation-- or any particular church or canon of books.
(2) The Muratorian Fragment itself notes that the so-called Apocalypse of Peter is not read in all the churches. That is one of the reasons it was later rejected. Most importantly...
(3) No church (including the Catholic Church, which I assume is the church you are referring to as "Rome") has ever pronounced the Muratorian Fragment as official de fide teaching, or pronounced that the list found in the Muratorian Fragment is the canonical one. Whoever told you that is just making it up and you should ask them for proof.
Yes, I know that it states that it was rejected by some, but what matters is what the church in Rome then thought.
It was in their canon -— their canon.
They didn’t possess infallibility then or now as the church in Rome was heretical with a Gnostic text within their canon of scripture.