insert() return null

Hello,
i using CI4 and i call method insert() and i set all required params but function return 0! why? how i can get error message if is exist!
My code is:

PHP Code:

namespace App\Models;
use CodeIgniter\Database\ConnectionInterface;
use CodeIgniter\Model;

class UserModel extends Model
{

    protected $table = 'users';
protected $primaryKey = 'id';
    protected $allowedFields = ['role', 'email','password','display_name','active','token'];
protected $useSoftDeletes = true;
protected $returnType = 'array';
protected $useTimestamps = true;
    protected $createdField  = 'created_at';
protected $deletedField  = 'deleted_at'; 


PHP Code:

$signup_email=$this->request->getVar('signup_email');
$signup_password=$this->request->getVar('signup_password');
$signup_password_confirmation=$this->request->getVar('signup_password_confirmation');
$val = $this->validate([
'signup_email' => ['label' => 'Email', 'rules' => 'trim|required|valid_email'], 
'signup_password' => ['label' => 'Password', 'rules' => 'trim|required'],
'signup_password_confirmation' => ['label' => lang('app.field_confirm_password'), 'rules' => 'trim|required|matches[signup_password]']
]);
if (!$val)
{

$validation=$this->validator;
$error_msg=$validation->listErrors();
$res=array("error"=>true,"validation"=>$error_msg);
}
else{
$UserModel=new UserModel();

$data = [
 'display_name' => $signup_email,
 'email'  => $signup_email,
 'password'  => md5($signup_password),
 'role'=>'customer',
 'active'=>'no'
 
 ];
$user_id =$UserModel->insert($data);
$res=array("error"=>false,"validation"=>$user_id);

} 


returns - bool - TRUE on success, FALSE on failure

I would double check your coding.

What did you Try? What did you Get? What did you Expect?

Joined CodeIgniter Community 2009.  ( Skype: insitfx )

returns - bool - TRUE on success, FALSE on failure

I would double check your coding.

 is return true but nothing added in table users in DB!!

 is return true but nothing added in table users in DB!!

If it returns 0 (like you said in the start) then it is returning false. 0==false

 is return true but nothing added in table users in DB!!

If it returns 0 (like you said in the start) then it is returning false.  0==false

how i can know what's the error exactly? have method to return sql  error?