the Muratorian Fragment represented the canon of scripture for Rome c. 180 A.D. (Some place it earlier).
This Canon has the NT within it minus some missing pieces, but also included the Revelation (Apocalypse) of Peter, a book that was a Gnostic text.
How could infallible Rome possibly have a Gnostic text within their approved Canon? Because they weren’t infallible on matters of faith as this scripture was right under their nose, right in their own back yard.
They had a penchant for declaring others to be “heretics” while they themselves were “heretics.”
There was no canon until after 300 A.D.