(Solved) Windows 10 Can't stop Windows from going to sleep mode

Windows is probably not going into sleep mode, it is probably just powering the video monitor off. That will happen on a schedule even if the system itself is still fully active, unless it is receiving user input. There is a setting for turn off display after..., that is what you need to set. There used to be a "never" option, but the max may be 3 hours in W10.
 
http://www.isunshare.com/windows-10/choose-when-to-turn-off-display-on-windows-10.html
 

Sleep and screen are two different settings.

So you have turn off display set to never appropriately? If so then another possibility is that Windows is switching to a screen saver, and the thing it is trying to use as a screen saver is either a black screen or a screensaver app that is no longer available on the system. To test it set up an available screensaver. If the screensaver appears instead of a black screen you have the answer.
 
http://www.thewindowsclub.com/customize-screensaver-settings-windows-10
 
btw: Check you computer's documentation. On most machines the power light will blink on at intervals if it is in sleep mode. Waking from hibernation is pretty obvious--not just an instant on after a mouse movement.

OK so what happens if you have the screensaver set to some visible screensaver, and the time to screensaver set to a large number? 
 
Have you definitely determined that you are not going into sleep mode? Have you determined that this is timer operated ie exactly the same elapsed time with each episode?
 
There are also settings in the BIOS, motherboard drivers, motherboard makers supplied utility applications, graphics adapter drivers and display drivers that can be applying power saving features. So what motherboard, what display etc. etc.? An installation of Windows 10 might well have replaced or hosed some of those, or it might be set to interact differently with your BIOS features or graphics adapter than your previous OS. 

Ampfixer may be right about it not being a malfunction. But it is not expected behavior if the display is set to never turn off. More to the point, you are looking at potentially hours of troubleshooting for a problem that is not really a problem in most cases. The reason the display settings are available to turn off when there is no user input for a period is that in most cases if there is nothing the user is doing there is no point in watching the screen. If you are at your keyboard when the screen blanks, and can instantly view it with a flick of the mouse, you can just do that. If you are not at the keyboard when the screen blanks, then you are not being annoyed by it. There certainly could be circumstances where you would crash your heavily armed drone into an elementary school if you were unable to see the screen for a second, but you have to ask yourself if that is what you are dealing with.

That sounds like it is a feature of the monitor rather than the OS. As mentioned above, my secondary monitor shifts itself to standby immediately on loss of input. The monitor may also have a "static input" standby in it (ECO settings?)

You must have different default settings than you had before. Mine is set to behave exactly as your machine. I'm still learning Win 10 so I'm not sure where that setting is. It seems that many of my Win 7 settings transferred over, but not all.

First screen for editing a power plan has as the first item: "turn off the display."
 
It is also listed as Display in the advanced power settings.
 
Setting to '0' is the same as 'never.'

So sounds like toggling the settings fixed it... yes?

Hello, guys. Thanks for your such nice post. Actually to say, I didn't meet the trouble that you described on your post. To Windows 10, there are some errors on it before. Such as Windows 10 blue/black to death, Windows 10 crashing, freezing and how to sue a Windows password key to recover Windows 10 password. But I don't know the trouble about Windows sleep mode. Sorry to say that I can't help you.