The Ascension of Isaiah mentions unknown Hebrew prophets named Aged, Ananias & Josab. Why did they not get canonical status?
The so-called Ascension of Isaiah is an apocryphal book. One thing we can know with certainty is that it was not written by Isaiah (and therefore it is pseudepigraphal, ie. falsely attributed), as scholars estimate it was written in the late first century AD or the early second century AD. The falsely-attributed Ascension of Isaiah was written in Greek, not Hebrew.
It is therefore rather obvioius why the Ascension of Isaiah was not ever even remotely considered for canonical status by the Jews. It is also rather obvious that the supposed “unknown” Hebrew prophets mentioned in this apocryphal book are not even real people, never mind potentially canonical prophets.
It is surprising that this proposal even came to you that these ought to have been given canonical status. I suspect this came from a Muslim source, as Muslim apologists have been trying to spread confusing misinformation about the Old Testament quite a bit recently. You can safely shelve this question.