Best Answer UnderMiner , 30 June 2019 - 01:47 PM
Windows update found and applied one more .NET update and I rebooted the server.
I allowed full privileges to all library folders for the local administrator account (was previously read, write, and execute).
The playback on Apple TV is now corrected.
For reference, I was using windows PC software Emby Theater version 18.104.22.168 with 22.2MBGo to the full post