Three Things which Prevent Duas being Answered

The Prophet (pbuh) and the Quran mentions that every dua is responded to. Either Allah gives you what you want, He gives us something equivalent or He averts something bad from our path. 

There are three ways in which our duas get rejected. Allah does not accept the dua from the one who’s heart is oblivious, meaning if your heart is not in the dua you are not making dua.

If you are just saying things like a parrot and mumbling phrases Allah does not accept these duas.  

When you make dua it is better to make it in your own language, from your heart, rather than in a language you do not know. 

Dua is a Gracious Gift From God: Use it Wisely!