To avoid any typo Please try to replace your fetch.php by https://raw.github.com/seblucas/cops/master/fetch.php
And edit your config_local.php to update these 2 config items :
$config['calibre_internal_directory'] = '';
$config['cops_x_accel_redirect'] = "";
There is no cache in COPS so the only thing I can think of is browser cache but I guess you tried CTRL+F5 many times.