Henry,
Thank you for your message.
To my surprise, upgrading MeshCommander from 0.6.3 to 0.6.4 solved the problem. I can access AMT Remote Desktop without any changes to the firewall or anti-virus. Note that I am using normal MeshCommander software (www.meshcommander.com/meshcommander), not the firmware, which requires AMT 11.6 or higher.
What I still don't understand is why a new Lenovo machine has an installer available for the Intel Management Engine Components, but this older Lenovo desktop does not offer that installer. Is this a generic Intel app that I can install on any Windows 10 machine? I found Download Intel® Management Engine Driver for Windows 7*, 8.1*, and Windows® 10 but it does not list the 4th-gen i5-4570 as a supported processor.
Here's the app I am talking about in the list of programs on a new machine:
Here is the user interface for that app:
Thanks,
Mark