How to resolve composer autoloader not found error?
So, this is something that is a little bit wonky in the user interface for composer manager. The file path to where the autoloader should be gets generated automatically in reference to the drupal root of where you configure composer. If your live and development environments have different doc roots, as is likely with a shared host (e.g. /var/www/html/mysite vs /yourhost/public_html/blahblah, your path will be different and drupal won't know where to look. To solve this problem you have to modify the composer manager file directory variable to reflect where the file actually is. You can't change this through composer manager's settings tab, because it will generate a site error that prevents navigating to the tab and editing it there. You can most easily edit this variable with the devel module's variable editor function.