I tried this on 3 different platforms: my laptop, PC, and digitalocean.
Everytime I try to verify the webhook address on Facebook for https://<YOUR_HOST>/webhooks/facebook/webhook. In my case <YOUR_HOST> is the ngrok URL for my PC/Laptop, and the webserver address for digitalocean - Facebook cannot reach the URL.
I have even tried it with the port numbers (5002 and 5005). Still no luck!
I can’t even resolve the URLs within my web browser - so I must be missing some step in the setup? What am I missing?