Reasons our Prayers are Unanswered
Have no Power with our God
1 Sam.15: 22 And Samuel said, Hath the Lord as great delight in burnt offerings and sacrifices, as in obeying the voice of the Lord? Behold, to obey is better than sacrifice, and to hearken than the fat of rams.
23 For rebellion is as the sin of witchcraft, and stubbornness is as iniquity and idolatry. Because thou hast rejected the word of the Lord, he hath also rejected thee from being king.
Here is a short list of the reasons why prayers are unanswered:
Disobedience #1 Reason: 
Deu.1:45 (1-46), Israel sent the 12 spies out to look into the promised lands and came back with a bad report, and discouraged the people so much they forgot to trust in the Lord their God who promised them that land. They forgot He was going to go with them and fight for them as well, so they suffered for forty years due to disobedience; (Our example of being left out of the Promised Land or in other words our Heavenly rewards~!~); 1 Sam.14:37; 1 Sam.15:22-23 (Saul Lost a Kingdom, for his disobedience; for the Lord looks at disobedience/rebellion, as if it were witchcraft & Idolatry!); and 28:6 And when Saul enquired of the Lord, the Lord answered him not, neither by dreams, nor by Urim, nor by prophets.
Ps.66: 18 If I regard iniquity in my heart, the Lord will not hear me: We see this even with King David and Bathsheba and their first born son who died because of disobedience to God’s commands, not to commit adultery; and God would not let their sin prosper and continue to grow, even though David fasted and prayed~!~
Prov.1:28 Then shall they call upon me, but I will not answer; they shall seek me early, but they shall not find me:
29 For that they hated knowledge, and did not choose the fear of the Lord:
30 They would none of my counsel: they despised all my reproof.
Neglect of Mercy:
Prov.21:12 The righteous man wisely considereth the house of the wicked: but God overthroweth the wicked for their wickedness.
13 Whoso stoppeth his ears at the cry of the poor, he also shall cry himself, but shall not be heard. (See Jms.2:13):
Despising the Law:
Prov.28:9 He that turneth away his ear from hearing the law, even his prayer shall be abomination. The thing to remember here is that every word out of the Lord’s mouth or one of His Prophets, or Apostles is a law and a commandment, seen in Jn.14:15; Jn.15:1-3; 14; and verse 20, that is tied directly to every word in this Holy Sacred word of God seen in Jn.10:35 for the words of God cannot be broken and will endure for all eternity, as well as not come back void from that which they were sent out to accomplish, Is.55:1-13~!~ See 2 Pt.1:19 We have also a more sure word of prophecy; whereunto ye do well that ye take heed, as unto a light that shineth in a dark place, until the day dawn, and the day star arise in your hearts:
20 Knowing this first; that no prophecy of the scripture is of any private interpretation.
21 For the prophecy came not in old time by the will of man: but holy men of God spake as they were moved by the Holy Ghost.
Is.1:15 And when ye spread forth your hands, I will hide mine eyes from you: yea, when ye make many prayers, I will not hear: your hands are full of blood. Look at all the abortions being done these days, and we allow vote after vote to be cast for the reduction of our own blood in our newborns every day we allowed those laws to pass in our lands~!~ Not to mention war after war we allow our politicians to conduct with our own sons and daughters being slain to the gods of this world called liberty and freedom as well as patriotism, when the Lord told us what we are to do with our enemies seen in Mt.5:38-48, if we want to be perfect as He is perfect; as Paul has shown us himself in Ro.12:1-21 as well~!~
Is.59: 2 But your iniquities have separated between you and your God, and your sins have hid his face from you, that he will not hear.
Mic.3:4 Then shall they cry unto the Lord, but he will not hear them: he will even hide his face from them at that time, as they have behaved themselves ill in their doings.
Zech.7:13 Therefore it is come to pass, that as he cried, and they would not hear; so they cried, and I would not hear, saith the Lord of hosts: (See 1 Sam.15:22-23 here as well):
Jms.1:6 But let him ask in faith, nothing wavering. For he that wavereth is like a wave of the sea driven with the wind and tossed.
7 For let not that man think that he shall receive any thing of the Lord.
8 A double minded man is unstable in all his ways.
Jms.4:1From whence come wars and fightings among you? Come they not hence, even of your lusts that war in your members?
2 Ye lust, and have not: ye kill, and desire to have, and cannot obtain: ye fight and war, yet ye have not, because ye ask not.
3 Ye ask, and receive not, because ye ask amiss, that ye may consume it upon your lusts.
4 Ye adulterers and adulteresses, know ye not that the friendship of the world is enmity with God? Whosoever therefore will be a friend of the world is the enemy of God.
 I have taken this from the Thompson Chain Reference Study Bible, pages of study of Prayer are from 1495-1498, topic #’s 2815 Spiritual Traffic: to 2840 Importunity in examples; the commentaries are my own. Rev. G. L. Boyett of Lord’s Way Ministries International & Bible College/ Professor of Systematic Theology/Doctrines and Law/Commandments.