Solved Can't shutdown or sleep with Nvidia GPU installed (works with AMD)

I have a very weird issue that I've never encountered. Long story short - Got a shiny new graphics card (Nvidia RTX 3070), and computer won't shut down, restart, or sleep with it installed (or any Nvidia GPU). It hangs at 'shutting down' and 'restarting' screens, and won't wake from a black screen while sleeping (the computer never actually reaches sleep, the keyboard turns off, but the fans & RGB don't ever shut off). I have to manually power down the computer to get it to turn off.

When I use an AMD card, the computer works fine, shuts down, sleeps, and restarts properly.

I've tried another Nvidia card (GTX 1050), same issue. Can't shut down or wake from sleep. So it's definitely an issue with Nvidia hardware or software

When I uninstall the Nvidia driver (using Windows basic display adpater), the computer shuts down properly. As soon as the driver is installed it is unable to shut down or sleep.

Things I've tried:
- Completely uninstalling graphics card drivers in safe mode (with DDU, removing AMD and Nvidia)
- Ran the power troubleshooter
- Disable fast startup
- Unplugging all peripherals
- Updating motherboard bios
- Playing around with some power & pcie settings in the bios
- Powercfg /energy offers "Platform Power Management CapabilitiesCI Express Active-State Power Management (ASPM) Disabled. PCI Express Active-State Power Management (ASPM) has been disabled due to a known incompatibility with the hardware in this computer.". Although I can't figure out what to do to troubleshoot this as I've already removed all hardware possible and the issue persists (not to mention that it is isolated to Nvidia drivers installed).

The Nvidia cards and system run fine otherwise. Games work great. I just can't think of what to try next to solve this power/shutdown/sleep stuff.

Any PCIe gpu power gurus out there able to help me out?

Ohmygosh I think I just solved it! Troubleshooting all day (I'm willing to spend hours trying everything imaginable except reinstalling windows, as usual!) I went through all my drivers to check for updates. Did quite a few, but once I updated my chipset drivers and my Intel RST drivers (I have an Optane accelerated storage drive), I was able to shut down and restart (and sleep!). It's working now as far as I can tell. I still can't explain why the Nvidia cards caused this behavior while AMD cards didn't, but I'm pretty sure it was updating either the Chipset and RST drivers that did the trick. Hope this helps anyone with the same issue.