ion auth with CI2.x

i  setup code locally from server but when i am trying to login ,welcome  page appears for micro seconds only due to session timeout .
the token and user have been verified for existence in the DB. The code is crashing as soon as it hits query under ion auth function.

You might want to move to CI 3.1.8, PHP 7.0 and the latest Ion Auth release.

You might want to move to CI 3.1.8, PHP 7.0 and the latest Ion Auth release.

this is the code :
$this->db->select('column name');
$this->db->from('oc_access_token');
$this->db->where('token',$access_token);
$this->db->where('atuser_id',$user_id);
$query = $this->db->get();
$result = $query->row();

the data(user id  and acess token) exiost in db but result is always null can you help me why result is null