you’ll find useful hints in the Collabora integration guide
familiarize yourself with the technologies you use e.g. https://docs.docker.com is good starting point for Docker systems . it will help you troubleshoot and solve issues sooner than later…
you can’t ping an URL! you can ping an IP/hostname but not an URL… one can use wget/curl to access the URL from the command line but this is a different story. …and for WOPI it makes huge difference where you access the URL from.