fatal error in DOMDocument

Fatal error: Uncaught Error: Class ‘DOMDocument’ not found in /var/www/21nfconf.com/wp-content/plugins/ilab-media-tools-premium/lib/mcloud-ivopetkov/html5-dom-document-php/src/HTML5DOMDocument.php:15 Stack trace: #0 /var/www/21nfconf.com/wp-content/plugins/ilab-media-tools-premium/lib/mcloud-ivopetkov/html5-dom-document-php/autoload.php(20): require() #1 [internal function]: {closure}() #2 /var/www/21nfconf.com/wp-content/plugins/ilab-media-tools-premium/classes/Tools/Integrations/PlugIns/SmartSliderIntegration.php(55): spl_autoload_call() #3 /var/www/21nfconf.com/wp-includes/class-wp-hook.php(292): MediaCloud\Plugin\Tools\Integrations\PlugIns\SmartSliderIntegration->filterContent() #4 /var/www/21nfconf.com/wp-includes/plugin.php(212): WP_Hook->apply_filters() #5 /var/www/21nfconf.com/wp-includes/post-template.php(253): apply_filters() #6 /var/www/21nfconf.com/wp-content/themes/Avada/page.php(24): the_content() #7 /var/www/21nfconf.com/wp-includes/template-loader.php(106): include(‘/var/www/21nfco…’) #8 /var/www/21nfcon in /var/www/21nfconf.com/wp-content/plugins/ilab-media-tools-premium/lib/mcloud-ivopetkov/html5-dom-document-php/src/HTML5DOMDocument.php on line 15

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