Once activated, this plugin generated a shortcode [tracking-fedex-usps] that you can insert into any post or page. The shortcode will be displayed as a shipping tracking page on the front-end. Provided tracking numbers for selected carrier (Fedex or USPS), it can track the shipping information.
For Linux server to use Fedex tracking, we need to install SoapClient by sudo apt-get install php7.0-soap; then sudo service apache2 restart.