$this->form_validation->run() returns FALSE

Why did not insert my message in Database? But false is working .

array(5) {
["name"]=>
string(18) "Md Nababur Rahaman"
["email"]=>
string(19) "[email protected]"
["subject"]=>
string(48) "How can i show individual tag id from tags array"
["message"]=>
string(37) "dssdf sdf df sd sdfsd a sf sdfsdfs fd"
["submit"]=>
string(0) ""
}