PayPal failure in v2.6.20

[huynguyen1210]

I'm using Virtuemart 2.6.20. The payment method is paypal standard When I place order, it redirects me to paypal gate. If I cancel the payment, it goes back to website and the order status is changed from pending to canceled. But when I make payment (completed), it doesn't go back to website and order status is not changed to "comfirmed"

When I enabled log, it shows
[return]   ⇒   http://natur.vyvijime.cz/index.php?option=com_virtuemart&view=pluginresponse&task=pluginresponsereceived&on=1-3541&pm=1&Itemid=293&lang=
[notify_url]   ⇒   http://natur.vyvijime.cz/index.php?option=com_virtuemart&view=pluginresponse&task=pluginnotification&tmpl=component&lang=
[cancel_return]   ⇒   http://natur.vyvijime.cz/index.php?option=com_virtuemart&view=pluginresponse&task=pluginUserPaymentCancel&on=1-3541&pm=1&Itemid=293&lang=

Is notify url normal? There is no order number there.