Man has turned from God and refuses to talk with Him.
Any time man chooses, God will listen and respond.
You know, most of us here were theists once. Most of those were christians. AFAIK nobody here got your god to listen and respond to their prayers. How do you explain that? And note that claiming we weren't "truthful" or "real christians" will just get you smacked so hard you'll see stars.
Not humble enough before God. No particular denomination of faith is required. I think Christian denominations are particularly poor at teaching prayer. I've never been to one that taught that prayers will (actually) be answered. They usually teach prayer then shrug their shoulders. And I get the impression that faith healers are looney just like others do.