I'm not sure what to think at this point. Everywhere I've gone to ask and everything I've tried is suggesting that the problem is with the PSU.
 
Unfortunately it takes time to actually replicate the problem, but when I leave my computer turned off for a few hours it seems that when I come back it will not power from the case power button or the power button on the motherboard unless I flip the power supply switch off for a few seconds. Beyond this, everything in my computer seems to be working normally.
 
To test this I would shut down the computer for approximately 3-4 hours and each time it would fail to power on when using the G2 until I flipped the PSU switch off and on. I've tried this three times with two other old power supplies and I haven't experienced the same problem with them. The other two power supplies were a Corsair TX750w and a Corsair CX750M.
 
In the event that this happens, the motherboard appears to still be receiving power, as the on-board power switch LED is still lit, as well as the mouse LED and an External drive LED.
 
I've already gone through getting a replacement through Amazon, but the second one I received seems to have the same exact problem. So either I've gotten two different power supplies that have the same defect, or there's something I'm just completely missing here. Can anyone give me an idea of something I might have done wrong? I'm at a loss here.
 
OS: Windows 10 Home
GPU: EVGA GeForce GTX 1070 SC GAMING
CPU Cooler: Cooler Master Hyper 212 EVO
Case: Cooler Master Storm Scout 2
PSU: EVGA SuperNOVA 650 G2
Motherboard: ASUS Z170-A
CPU: Intel Core i5 6600K
RAM: Ballistix Sport LT 8GB Kit (4GBx2) DDR4
SSD: Crucial MX300 275GB SATA 2.5 Inch Internal Solid State Drive - CT275MX300SSD1
Secondary Hard Drive: WD Blue 1TB SATA 6 Gb/s 7200 RPM 64MB Cache 3.5 Inch Desktop Hard Drive (WD10EZEX)

bcavnaugh
Welcome to the Forum
After Two PSU I would be looking at your Motherboard: ASUS Z170-A and or Computer Case.

Any particular reason the motherboard might not play nice with this specific power supply when it is with others?

bcavnaugh
Take your MB out of the Case and Run a Bench Test for a few Days.

Sounds a tad excessive. Should I test this with the power supply that's having issues or the ones that aren't?

bcavnaugh
Turn Off (Disable) Power Management in your Bios and in Windows 10. Sounds like your MB and OS are not walking up.

Ok, I admit I'm pretty dense, but how does this relate to the OS when it's a matter of it simply not powering on? It does nothing at all when I hit the motherboard's own power switch, even with my drives and everything else disconnected. I'll check to see if there's something in the BIOS, though. Edit: Power saving options were disabled as far as I can tell.

bcavnaugh
Also I hope that you DID Remove all the Older Power Supplies Cable From your Computer Case and installed ONLY the NEW Cables that came with your New Power Supply.

When I returned the previous PSU to Amazon I obviously sent the cables with it. So no that's not the problem. Unless you were talking about the other two I tested, but those aren't even modular.

Well. I tried sitting it outside of the case and it didn't give me trouble after three hours. I find that odd, given that the other two power supplies had no issue in the case and now I'm not reproducing with the evga outside of the case. Maybe there's some other factor I've overlooked.
 
I do have to bend the motherboard power cable a bit to fit them through the back of my case, could that be an issue? I'll try refitting it with the cables run through the front and wait through the night on it.