Why does uploading images fail in this application?

Have you tried checking each suitable points ? For example, after your upload path line you can :

PHP Code:

$config['upload_path'] = './assets/img/avatars';

echo $config['upload_path];
die();
// or print_r() where suitable.. 


So that you can see the results of each code block.

By the way, $this->load->library part did not work for me as well and I used it as below in one of my projects:

PHP Code:

//$this->load->library('upload', $config); instead of this, use below
  $this->upload->initialize($config); 


Nice, but how do I load the upload library then?