Thank you for your response.
To close the loop, this ended up being an issue with inbound firewall rules on the server. When we removed IIS it removed the inbound rule for 80/443. The dead giveaway was that we could navigate to https://localhost:443/monitor and the monitor displayed properly.

Additionally (and this was news to me), I had copied down a directory from the demos which (I thought) contained the monitor. This was causing issues by having the same name as the internal monitor. I simply deleted the directory and all was well with the internal web server.

Thanks again.