Gravity Forms Error

There is a simple fix for this without upgrading Gravity Forms, but you'd have to edit a plugin file for Gravity Forms.

in notification.php, in the class

GFNotificationTable extends WP_List_Table {...

Add this method:

    function get_columns() {        $columns = array(                'name' => 'Name',                'subject' => 'Subject'                );        return $columns;    }

The same solution can be applied to any plugin where you're seeing this problem. The columns array just needs to match the names set as $this->_column_headers.

Adding to the previous answer, to fully fix the problem you'll need to also place that same function:

function get_columns() {        $columns = array(                'name' => 'Name',                'subject' => 'Subject'                );        return $columns;    }

In the GF form_settings.php file under the class GFConfirmationTable extends WP_List_Table.

The first fixes the Notifications error and this fixes the Confirmations error.

I figured it out. Once I put the license key into the settings, I was able to download the update. Installed and the error went away.