Plugin access

I try to use a class from your plugin from a custom plugin. Whenever the following code runs I get an error:

$orderid = substr($ordernrexternal, $prefixlength);
// Check if seq order number plugin is active
if (function_exists(‘wc_seq_order_number_pro’)) {
$orderid = wc_seq_order_number_pro()->find_order_by_order_number($orderid);
} elseif(class_exists(‘wc_seq_order_number’)) {
$seq = new wc_seq_order_number();
$orderid = $seq->find_order_by_order_number($orderid);
}

This line $seq = new wc_seq_order_number(); causes the error:

Uncaught Error: Class ‘xxx\xxx\URLEndpoints\wc_seq_order_number’ not found in /var/www/clients/client1026/web5168/web/wp-content/plugins/…/OrderImporter.php:324

Obviously the class can not be instantiated because my plugin can’t find it.

Any suggestions how to solve this issues are highly welcome.

Thanks in advance and kind regards,

Reto