Shortcode not working on my theme

Everything seems to be okay. I’ am also using function for the Shortcode

<?php echo do_shortcode("[event_calendar]"); ?>

Also this scripts are loaded
fullcalendar.min.js

jQuery is loaded in the header.

When its renders in the page, Its shows up this this – [event_calendar]

https://www.ads-software.com/plugins/wp-calendar/