Let me explain a little. When we need to process a credit card we start by connecting with the gateway and asking the gateway if we can send a request. That's called a handshake. When the gateway respond all is ok we continue to sent them the request to charge a credit card and the gateway needs to respond if it's approved. In the rare case that the handshake went thru correctly but we never received a response from the gateway if the card is approved we stop the credit card service from continuing until we manually check if the card went thru or not. Further attempts can just aggravate the situation as it might lead to multiple transactions charged on the user credit card.