my ROG Crosshair VIII Dark Hero won't wake up if it sleeps for a few hours. No problems when I wake it within a few minutes, 30 minutes or so, no idea. If it won't wake up, pressing the power button or reset button won't work too. I have to power off the PSU and press the power button for ~15 seconds until the power is totally gone. WOL works within the small time limit and stops working if the PC sleeps for a few hours (doing nightly backups automatically using WOL, RTC would be an option too).
I am using a be quiet! Dark Power 12 (1000 W) PSU, RTX 3080, Ryzen 5900X. Default BIOS settings. Currently testing ERP (enabled), maybe this will solve it, but I don't think so.
I changed to the Dark Hero from a Gigabyte Aorus Master because the MB made trouble (sometimes 2,5 Gbit LAN is gone, sometimes BIOS navigation super slow and so on). Sleep mode worked perfectly with the Aorus Master.
Also did a fresh install of Windows 10 (latest version) + drivers and so on. Next is to test a longer hibernate state instead of sleep (but hibernate takes too long to wake up).