Short answer
Every sincere dua is answered, but not always in the form you expect. The Prophet ﷺ said Allah either gives what you asked, keeps an equal harm away from you, or stores it as reward for the Hereafter. Things that block a dua include haram income, asking for sin, and giving up by saying "I prayed and was not answered".
There is no special fiqh ruling here. The scholars of all schools list the conditions of dua: sincerity, halal food and earnings, not asking for sin or cutting family ties, and patience without despair.
The four schools agree on this.
Explanation
How Allah answers. The Prophet ﷺ said that no Muslim on earth calls on Allah without Allah giving it to him, or turning away from him an equal harm, as long as he does not ask for sin or the cutting of family ties (al-Tirmidhi). Another narration adds that the reward may be saved for the Hereafter. So a dua that seems unanswered may have kept a disaster away, or be waiting as reward. Allah also says you may dislike a thing that is good for you (2:216).
Things that hold a dua back:
- Impatience: "Your dua is answered as long as you are not hasty, saying: I prayed and was not answered" (Bukhari). Keep asking.
- Haram income: the Prophet ﷺ described a dusty traveller raising his hands to the sky saying "O Lord, O Lord", while his food, drink and clothing were haram, and asked how he could be answered (Muslim).
- Asking for sin or for harm to family ties.
- A heedless heart: words said without attention or certainty.
What to do: make tawbah, check where your money comes from, begin with praise and salawat, use the times of acceptance, and keep asking with good expectation of Allah. Zakariya asked for a child into old age, and Yaqub waited years for Yusuf. Dua is worship in itself, so even the asking is rewarded: see what is dua.
The evidence
Quran, Surah Al-Baqara 2:186
وَإِذَا سَأَلَكَ عِبَادِى عَنِّى فَإِنِّى قَرِيبٌ ۖ أُجِيبُ دَعْوَةَ ٱلدَّاعِ إِذَا دَعَانِ ۖ فَلْيَسْتَجِيبُوا۟ لِى وَلْيُؤْمِنُوا۟ بِى لَعَلَّهُمْ يَرْشُدُونَ ﴿١٨٦﴾
And when My servants ask you, [O Muhammad], concerning Me - indeed I am near. I respond to the invocation of the supplicant when he calls upon Me. So let them respond to Me [by obedience] and believe in Me that they may be [rightly] guided.
Allah promises to answer.
Quran, Surah Al-Baqara 2:216
كُتِبَ عَلَيْكُمُ ٱلْقِتَالُ وَهُوَ كُرْهٌۭ لَّكُمْ ۖ وَعَسَىٰٓ أَن تَكْرَهُوا۟ شَيْـًۭٔا وَهُوَ خَيْرٌۭ لَّكُمْ ۖ وَعَسَىٰٓ أَن تُحِبُّوا۟ شَيْـًۭٔا وَهُوَ شَرٌّۭ لَّكُمْ ۗ وَٱللَّهُ يَعْلَمُ وَأَنتُمْ لَا تَعْلَمُونَ ﴿٢١٦﴾
Fighting has been enjoined upon you while it is hateful to you. But perhaps you hate a thing and it is good for you; and perhaps you love a thing and it is bad for you. And Allah Knows, while you know not.
What you asked for may not be best for you.
Jami' at-Tirmidhi 3573
Grading to be checked... ما على الأرض مسلم يدعو الله بدعوة إلا آتاه الله إياها أو صرف عنه من السوء مثلها ...
"There is no Muslim on earth who calls on Allah with a dua except that Allah gives it to him or turns away from him an equal harm."
Every dua is answered in one of several ways.
Sahih al-Bukhari 6340
Sahih... يستجاب لأحدكم ما لم يعجل يقول دعوت فلم يستجب لي ...
"Your dua is answered as long as you are not hasty, saying: I made dua and it was not answered."
Giving up is a reason a dua is held back.
Sahih Muslim 1015
Sahih... الرجل يطيل السفر أشعث أغبر يمد يديه إلى السماء ...
"He mentioned a man on a long journey, dishevelled and dusty, stretching his hands to the sky, while his food and clothing were haram; so how can he be answered?"
Haram earnings block dua.
Checked by our team. For a more accurate answer to your own situation, consult a scholar. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.