Fatal error: Call to undefined function curl_setopt()

Seems there's no curl installed on your server. Check your phpinfo() for curl. If not present, you or your provider can enable it in the PHP config:

/etc/php5/apache2/php.ini (or similar)

enable extension:

extension=curl.so

I had same issue just install curl and restart your ngix or apache and php5

sudo apt-get install php5-curl
sudo service php5-fpm restart

You need to enable the curl extension for PHP.