You will need to change some settings in your Worldpay account. Please follow the instructions below:
1. Login to merchant account at worldpay, edit the installation, in the Payment Response URL textbox, enter YOUR_SITE_URL/index.php?option=com_pmform&task=payment_confirm&payment_method=os_worldpay, for example,
joomdonation.com/index.php?option=com_pm...t_method=os_worldpay
2. Check on Payment Response enabled checkbox
Could you please do that and check it again ?
Tuan