CForm - Call to a member function error

I'm currently trying to fix a new form that I assume is being generated in the controller that broke when I updated the version of yiibooster and broke the functionality of their forms. I have inherited this from a developer who is no longer with the company and so I'm trying to make as little changes to the system as possible, as there is little documentation

I decided to just try and revert to CForm but I'm still getting this error

Fatal error: Call to a member function beginWidget() on array in /Applications/XAMPP/xamppfiles/htdocs/framework/web/form/CForm.php on line 437

Note, removing the null from my code returns a stack trace error of "beginwidget function does not exist in sessionForm", which is correct because it no longer is using the extension.

private function getSessionSelectionForm($dataModel) {
        // SessionSelection Form Model
        $sessionForm = new SessionSelectionForm();

        $items = $dataModel->getDynamicFormSessionsConfig($sessionForm);

        $form = new CForm (
                        array(
                    'title' => 'Session Registration',
                    'enableClientValidation' => true,
                    'enableAjaxValidation' => false, // Just keep this to false
                    'layout' => TbHtml::FORM_LAYOUT_HORIZONTAL,
                    'elements' => $items,
                    'buttons' => array(
                        'reset' => array(
                            'buttonType' => 'reset',
                            'label' => 'Reset',
                        ),
                        'submit' => array(
                            'buttonType' => 'submit',
                            'label' => 'Next',
                            'context' => 'primary'
                        ),
//                        'cancel' => array(
//                            'type' => 'submit',
//                            'label' => 'Cancel',
//                            'layoutType' => 'warning'
//                        ),
                    ),
                        ), null, array(
                    'htmlOptions' => array('class' => 'well'),
                    'type' => 'horizontal',
                        ), $sessionForm
        );

        return $form;
    }

And the view

<?php echo $form->render(); ?>