Support System Shortcode in a function

Hi

I have made some changes to my functions.php file to add a new endpoint for Support to the Woocommerce My Account page.

The function I am using to display content in this tab is:

// ------------------
// 4. Add content to the new endpoint
function revealws_premium_support_content() {
echo '<h3>Reveal Web Solutions Support</h3><p>Welcome to the Reveal Web Solutions support area. As a valued customer, you can submit a ticket should you have any issues with your website.<p><i>Please contact your theme/plugin developer for specific theme/plugin-related support.</i></p>';
echo do_shortcode('[support-system-tickets-index]');
}
add_action( 'woocommerce_account_premium-support_endpoint', 'revealws_premium_support_content' );

Although the html content displays correctly and it creates a container called <div id="support-system"> the container is empty.

The shortcode works correctly on a page just not in this function.

Any ideas why?