Missing a temporary folder not fixed

  1. You need to add that line to your wp-config.php. Double check that you put it in the right place.
  2. You need to set the permissions on that directory you created so that WordPress can write to it. This is dependent on how your hosting works and what program you’re using, but you should try setting the permissions to e.g. 770, which gives write permission to both the user and group.