Asalamu alaikum...
It happens sometimes that the dua doesn't get accepted readily or you dont see the effect immediately... this can be due to a wrong way of making dua(or asking something that is not good) or it is a test from Allah subhana wa taa'la...
sometimes the calamity you are afflicted with makes you to come closer to Allah and Allah wants good for you...
I have learnt that other than the specific time , there are a lot many other things needed for the acceptance of dua...
It was narrated that Faddalah ibn ‘Ubayd said: The Prophet (peace and blessings of Allah be upon him) heard a man making dua after his prayer, but he did not send blessings upon the Prophet (peace and blessings of Allah be upon him). The Prophet (peace and blessings of Allah be upon him) said: “This man is in a hurry.” Then he called him and said to him or to someone else: “When any one of you has finished praying (and makes dua), let him start by praising Allah, then let him send blessings upon the Prophet (peace and blessings of Allah be upon him), then after that let him ask for whatever he wants.” Al-Albani said: it is a saheeh hadeeth. (Saheeh Sunan al-Tirmidhi, 2765.
The Prophet (peace and blessings of Allah be upon him) said: “The slave will receive a response so long as his dua does not involve sin or severing of family ties, and so long as he is not hasty.” It was said, “What does being hasty mean?” He said: “When he says, ‘I made dua and I made dua, and I have not seen any response,’ and he gets frustrated and stops making dua.” Narrated by al-Bukahari, 6340; Muslim, 2735.
Dua signifies the faith in Allah...