OK. It looks like the root cause was Windows Defender Firewall. I haven’t absolutely verified this, but I’m confident. On the new VM, when ar000.exe starts, Defender pops up a dialog to allow ar000.exe to open ports. On all other machines I’ve tried, the dialog never appears. I’ve seen this dialog pop up in many videos I watched while troubleshooting this problem, but I always assumed that I didn’t see it because the firewall is listed as off for all networks:
But, apparently sometimes OFF isn’t really off. I’ll have IT check into it and if that doesn’t fix things, I’ll report back. Otherwise, I would consider this solved.