Hi Saket,
The following suttas give reasons as to why one may not attain a magga pala even when when listening the true Dhamma.
https://suttacentral.net/en/an6.86
https://suttacentral.net/en/an6.87
https://suttacentral.net/en/an6.88
I have listed them down below:
He is endowed with a kamma obstruction, a defilement obstruction, a result-of-[past]-kamma obstruction(kamma-vipaka); he lacks conviction, has no desire [to listen], and has dull discernment, and while listening he does not listen well, does not give ear, does not apply his mind to gnosis, grabs hold of what is worthless, rejects what is worthwhile, and is not endowed with the patience to conform with the teaching.