Not receiving alert from API

I am using flight API alert service to set alert, the alert is getting properly set and we are also receiving alert id. But we are not receiving any push notification from Flightaware when the flight is departing or arriving.
Please note, earlier we were getting push notifications from Flightaware using the same code, but now we are not receiving any more alerts.

Your alerts are failing to be delivered because your webserver is taking too long to respond. We require that the endpoint URL that you register with us be able to respond to a delivery attempt within 5 seconds.

You can view the status of the last few delivery attempts here, and initiate some manual delivery attempts to test your backend: flightaware.com/commercial/flightxml/send.rvt

Thanks for the reply. Got the problem, we were setting the source airport incorrectly.