Hi Max,
This issue do not directly related to our plugin. Possible it is some issue with your hosting.
You can find more information in the articles below:
https://wordpress.org/support/topic/does-not-work-437?replies=10
http://forum.virtuemart.net/index.php?topic=132261.0
We hope this information will help you.
with king regards,
WordPress Webcodin Team