When you have been asking for a long time
God hears every prayer. The Qur'an puts it without hedging: "I am near. I answer the call of the one who calls when they call on me." That promise is the reason unanswered dua hurts the way it does. If you had never been told anyone was listening, silence would mean nothing. You were told, and you have been asking a long time.
The people the Qur'an holds up as examples waited too, some of them for most of a lifetime. Zakariya asks for a child as an old man, bones weak and hair gone grey, and he says while still waiting: "never, my Lord, has my prayer to you gone unanswered." Ibrahim gives thanks for sons granted "in my old age." Neither man got a quick reply, and neither stopped asking.
Some of what the Qur'an says here is uncomfortable and worth sitting with anyway. We do not always know what we are asking for: "The human being prays for harm the way he prays for good…" And "You may hate something that is good for you, and you may love something that is bad for you." A no can be mercy wearing a face you do not recognise, which is easier to write than it is to feel at three in the morning.
Complaint is allowed. Ya'qub, blind from weeping, says "I bring my anguish and my sorrow to God alone" — the sorrow goes toward God rather than away from him. Yunus calls out from inside the dark and from inside his own admission of fault, and the answer comes: "So we answered him and delivered him from the distress." Scripture keeps both halves in the record, the crying out and the response.
When revelation itself paused and the Prophet was taunted for it, the verse that came said "your Lord has not forsaken you, nor is he displeased." A gap in the answering was no verdict on him. If you are in that gap now, the counsel here stays stubbornly ordinary: keep asking, keep the prayer, and let the wanting stay honest. Where it is trust you are struggling to hold, the verses on trust in God sit close to this; where the silence has hardened into something colder, the verses on doubt may be the better door.