PHP Fatal Error

When going onto my clients website, I keep getting this error:

Fatal error: Call to a member function removeLoopAddToCartLinksInSomeProducts() on a non-object in /home/medisymp/public_html/wp-content/plugins/woocommerce-prices-by-user-role/WooUserRolePricesFrontendFestiPlugin.php on line 870

I have looked into the PHP file but cannot seem to find any errors on lines 860-884, what am I doing wrong?

$settings = new SettingsWooUserRolePrices($this->_languageDomain);

        $options = $settings->get();

        $values = $this->getOptions('settings');
        if ($values) {
            foreach ($options as $ident => &$item) {
                if (array_key_exists($ident, $values)) {
                    $item['value'] = $values[$ident];
                }
            }
            unset($item);
        }

        return $options;
    } // end loadSettings

    private function _displayPluginErrors()
    {
        $caheFolderErorr = $this->_detectTheCacheFolderAccessErrors();

        if ($caheFolderErorr) {
            echo $this->fetch('refresh.phtml');
        }
    } // end _displayPluginErrors