custom pdf template failed

Hello, after updating to version 2.X, the customized pdf template cannot show up.

use FluentForm\App\Services\FormBuilder\ShortCodeParser;
use FluentForm\Framework\Foundation\Application;

class certificate extends \FluentFormPdf\Classes\Templates\TemplateManager
{
    public function __construct(Application $app)
    {
        parent::__construct($app);
    }

    public function getDefaultSettings() { return ['header' => '', 'footer' => '', 'body' => '']; }
    public function getSettingsFields() { return array(); }

    public function generatePdf($submissionId, $feed, $outPut = 'I', $fileName = '')
    {
        $submission = wpFluent()->table('fluentform_submissions')->where('id', $submissionId)->first();
        $response = json_decode($submission->response, true);

        

        

        $htmlBody = '
			
            <div class="description">
                test test test
            </div>
	';

        if (!$fileName) {
            $fileName = 'certificate -' . $submissionId;
        }

        return $this->pdfBuilder($fileName, $feed, $htmlBody, '', $outPut);
    }
}

error message as below

Uncaught Error: Class \”FluentFormPdf\Classes\Templates\TemplateManager\” not found in /var/www/wp-content/uploads/FLUENT_PDF_TEMPLATES/certificate.php on line 6″,”data”:{“message”:”Uncaught Error: Class \”FluentFormPdf\Classes\Templates\TemplateManager\” not found”,”file”:”/var/www/guide/event/wp-content/uploads/FLUENT_PDF_TEMPLATES/certificate.php”,”line”:6,”trace”:[{“file”:”/var/www/wp-content/plugins/insert-headers-and-footers/includes/class-wpcode-snippet-execute.php(419) : eval()’d code”,”line”:24,”function”:”include_once”}

But the code runs well in version 1.111

Thanks!