after joomla 5 update i receive this error:

Symfony\Component\ErrorHandler\Error\ClassNotFoundError: Attempted to load class "Helper" from namespace "HelixUltimate\Framework\Platform". Did you forget a "use" statement for another namespace?

at /var/www/html/deplazioblack/templates/wt_grandy_free/error.php:19 at require() (/var/www/html/deplazioblack/libraries/src/Document/HtmlDocument.php:731) at Joomla\CMS\Document\HtmlDocument->_loadTemplate() (/var/www/html/deplazioblack/libraries/src/Document/HtmlDocument.php:785) at Joomla\CMS\Document\HtmlDocument->_fetchTemplate() (/var/www/html/deplazioblack/libraries/src/Document/HtmlDocument.php:622) at Joomla\CMS\Document\HtmlDocument->parse() (/var/www/html/deplazioblack/libraries/src/Document/HtmlDocument.php:640) at Joomla\CMS\Document\HtmlDocument->render() (/var/www/html/deplazioblack/libraries/src/Document/ErrorDocument.php:139) at Joomla\CMS\Document\ErrorDocument->render() (/var/www/html/deplazioblack/libraries/src/Error/Renderer/HtmlRenderer.php:70) at Joomla\CMS\Error\Renderer\HtmlRenderer->render() (/var/www/html/deplazioblack/libraries/src/Exception/ExceptionHandler.php:136) at Joomla\CMS\Exception\ExceptionHandler::render() (/var/www/html/deplazioblack/libraries/src/Exception/ExceptionHandler.php:73) at Joomla\CMS\Exception\ExceptionHandler::handleException() (/var/www/html/deplazioblack/libraries/src/Application/CMSApplication.php:336) at Joomla\CMS\Application\CMSApplication->execute() (/var/www/html/deplazioblack/includes/app.php:58) at require_once('/var/www/html/deplazioblack/includes/app.php') (/var/www/html/deplazioblack/index.php:32)