Some templates providers modify the VirtueMart component itself, instead of doing template overriding. Some folders are removed from the component VirtueMart itself. The view Pluginresponse is the one used when the payment is accepted by the payment provider. If this folder does not exist, Joomla returns an error 500.In the picture below, on the left, are displayed the views from the original virtuemart component. On the rigth side, are displayed the views of the component virtuemart provided by the templater. In this case, the folders: invoice, manufacturer, orders, vendor, pluginresponse are missing.
Note that in this case, you cannot update VirtueMart, and benefit new features. We strongly recommend you to use another template provider.