Can't connect to web server, but can VNC, ping

I have a very simple setup - A Mac mini and an iPhone. I use the Mac mini as a local web server running with the service on port 5000 (I’ve tried port 80 and 8080 too). I can’t reach this when I’m remote, all I get back are “Can’t connect to server” messages from the browser. However, I CAN ping and start a VNC session with the Mac mini via ZeroTier with no issues. Since the other two services work, and the web service does not. I have no problems reaching the web server when I’m local.

I’m at loss as how to troubleshoot - anyone have any clues?