The only problem is that the Muratorian fragment represents the approved canon of scripture in Rome, c. 180 A.D.
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.
before you get any further carried away: from the wiki “In addition to receiving the Apocalypse of John into the church canon, the author remarks that they also receive the Apocalypse of Peter, although “some of us will not allow the latter to be read in church.” However, it is not certain whether this refers to the Greek Apocalypse of Peter or the quite different Coptic Apocalypse of Peter, the latter of which, unlike the former, was Gnostic.”
So it’s not quite that cut and dried.
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.