@SteveJonesGtr, yeap, it’s probably your ngrock tunnel. My teammate had a similar issue running a tunnel to his localhost. I don’t think location is going to be huge factor as we have developers up and running with webhooks in India, Middle East and Asia. Unfortunately, I’m not going to have an easy solution for tunnels. It’s a use case we have to discuss here. If you do find a fast tunneling service, please ping us.
As for a complicated solution you can do the following: Deploy a webapp that proxies requests to your ngrock tunnel. The webapp can handle the CRC GET request itself without proxying to your localhost. For POST requests the webapp should immediately respond with a 200 and then relay the request to your ngrock tunnel. You can achieve something similar with an AWS API Gateway and Lambda.