Sforno on Deuteronomy 1:45/ספורנו על דברים א׳:מ״ה

1ולא שמע ה' בקולכם, on account of the desecration of His name that was part of their sin. Whenever a sin includes חילול השם, the desecration of G’d’s name, (seeing that is by definition something public) forgiveness without death of the penitent sinner is impossible. Not only that, but G’d’s decree had been formulated as an oath, something that made it irrevocable after both Joshua and Calev had made efforts to make the people reconsider their negative attitude by accusing G’d of hating them. As a matter of fact, even when they did repent afterwards, this was not genuine, but was based on their fear of punishment. As a result, such a repentance is not sufficient to cancel the punishment due in this life. Something similar had already occurred with Kayin, who also repented but only because he could not face the punishment in store for him. (Genesis 4,15) Both King Shaul, in respect of his failure to wipe out Amalek completely, (Samuel I 15,26) and the High Priest Eli (Samuel I 3,14) repented, but did so only out of their unwillingness to face their punishment.

2ולא האזין אליכם. G’d did not even listen to your plea to delay the punishment, or to suspend the part of the punishment for their children after their parents had died. Moses used this fact as proof that the repentance of their parents at the time had not been complete, sincere. As a result, even their tears had been to no avail.