I have "solved" the issue - basically, Wake-on-Lan works from a power-off state as long as BIOS settings are correct (it has to be enabled in BIOS, and deep sleep in S4/S5 cannot be enabled), and assuming the network adapter settings (to allow wake on magic packet) are set in Windows. My problem was waking from sleep - and the issue really is that sleep on this machine is not S3 - standby that I was very familiar with, but S0 - "Modern" sleep. And I will say that for all practical purposes, wake-on-lan will not work with modern sleep, and modern sleep isn't at all what I would call sleep. The research I've done (with smart plug 5-second true power monitoring - Emporia smart plug) shows the PC will never really sleep (which I define as going into a ultra-lower power state preserving RAM and machine state only) and even if the registry changes are made to disable Modern connected sleep, the PC still will never sleep if almost any application is running. The PC will use nearly as much power as when I'm using it in normal operation in this modern sleep. This should be a crime - this push to everything always on/always connected, can't turn it off is ridiculous and contributes to the global climate crisis. So, my solution is: I've enabled hibernation and S4 is sleep, and I have totally disabled S0 sleep (registry entry:: HKLM\System\CurrentControlSet\Control\Power: Dword: PlatformAoAcOverride  Value:0) and set the PC to hibernate after [20] minutes. It takes about 20 seconds to resume from hibernation, which isn't as good as the 5 or so seconds I'd expect from S3, but it's the only thing that will work for me. And, despite instructions that say Wake-on-lan will not work with S4/hibernation enabled, it works just fine. I can do WoL to re-start from power off (S5) or hibernation (S4).  [I didn't expect WoL to work from S4, so my plan was to use the BIOS setting to boot after loss of power and use the smart power switch to disconnect AC after hibernating the machine - then could remotely restart the machine by turning the smart switch back on.)  
New Precision 3660 and trying to set up for Wake-on-lan.  Changed the BIOS to disable deep sleep in S4 and S5.  The machine turn on with the WOL magic packet if the computer is powered off, but it never succeeds if the computer is in sleep. When it is in sleep, the WOL signal does something (I hear the relay/click from the power supply) and the hard drive light flashes, and the LAN card is active and has IP address because RDP will try and connect - but the power light never comes on the PC, I hear another relay click as if power supply is going back off, and eventually I get an error message about licensing from the rdp client.  I think this is related to the really strange behavior of trying to wake the machine from sleep locally: if I press a key on the keyboard, the same power supply click as if it's going to come on happens, but the machine doesn't wake up. It takes pressing the keyboard key at least two, sometimes more times for it to actually fully wake up. I have repeated this test over and over and it is always the same - at least two keyboard presses to wake up - one is not enough. I've tried sending multiple WOL magic packets, but that doesn't help.  I have updated the BIOS, Windows update, checked every setting and am unable to resolve this issue.    
Precision 3660 WOL does not work