Fatal error: Uncaught Error: Class 'avia_auto_toc' not found

Hi
I added a while back the following code to display the TOC, with the help of you guys.

add_shortcode('toc', 'avs_toc_function');
function avs_toc_function() {
    $args = array (
        'name' => 'Displayed Everywhere',
        'id' => 'av_everywhere',
        'description' => '',
        'class' => '',
        'before_widget' => '<details>  <summary>Table of Contents</summary><section id="avia_auto_toc-2" class="widget clearfix avia_auto_toc">',
        'after_widget' => '<span class="seperator extralight-border"></span></section></details>',
        'before_title' => '',
        'after_title' => '',
        'widget_id' => 'avia_auto_toc_custom',
        'widget_name' => 'Enfold Child Table of Contents',
        );

    $instance = array (
        'title' => ' ',
        'exclude' => '',
        'style' => '',
        'level' => 'h2',
        'single_only' => 0,
        'indent' => 1,
        'smoothscroll' => 1,
        );

	ob_start();
	$toc = new avia_auto_toc;
	$toc->widget($args, $instance);
	$output = ob_get_clean();

	return $output;
}

After the latest update i get the error Fatal error: Uncaught Error: Class ‘avia_auto_toc’ not found
if i comment the code, the pages loads but the TOC is not showing.

I have a lot of posts that uses this shortcode to present the TOC.

Can you help figure out a solution.

Thank you