It sounds as though the computer went into sleep mode but i am not sure why it would not wake up when you hit a key or moved the mouse.

 

You could try changing the time for the computer to go into sleep mode or even prevent it from going into sleep just to complete the render.  To change the settings go to the control panel - hardware and sounds then the power options. 

 

 

 

 

I use Poser 13 on Windows 11 - For Scene set up I use a Geekcom A5 -  Ryzen 9 5900HX, with 64 gig ram and 3 TB  storage, mini PC with final rendering done on normal sized desktop using an AMD Ryzen Threadipper 1950X CPU, Corsair Hydro H100i CPU cooler, 3XS EVGA GTX 1080i SC with 11g Ram, 4 X 16gig Corsair DDR4 Ram and a Corsair RM 100 PSU .   The desktop is in a remote location with rendering done via Queue Manager which gives me a clearer desktop and quieter computer room.