Unable to Catch Webhook/Postback on our hosted Express.js Server

It seems that changing postback/webhook endpoints are not reflected immediately or maybe that the endpoint I've specified has been banned for some reason

I've tried changing ports , mapping ip to DNS however I still can't catch the postbacks on my hosted server, however postbacks can be caught by using service like requestcatcher.com

When do changes in postback URLs reflect and is there any case of banning IP address of webhooks if they are not configured properly