“One who turns away his ear from hearing the law,
even his prayer is an abomination.”
Proverbs 28:9

When you come to the most high God, you need to come in reverence before the Holy One, and in humility concerning his Word. Otherwise, your prayer is useless.

Does God ever reject prayer? Yes:

“If I regard iniquity in my heart,
the Lord will not hear.”
Psalm 66:18

If you turn to God when you need his help but live in deliberate sin – you may find yourself alone to solve your problems. Sin is rebellion. God will not hear the proud, nor the rebellious.

But if you humble yourself before the great God and come in humility and repentance, you will be lovingly received and you will receive mercy.

“He who covers his sins will not prosper,
but whoever confesses and forsakes them
will have mercy.”
Proverbs 28:13