There seems to be an ever increasing number of issues with Windows 11 and Linux (almost as if intended). Anyway, there may be something odd going on with Windows 11 Fastboot. Restart, log into Windows, completely shutdown, no fastboot. It locks filesystems etc. so I would not be surprised if more modern firmware's ACPI can be messed with, too.
Only other thing I can think is run systemctl suspend
in a terminal and see what errors it outputs. Could very well be an ACPI issue in Ubuntu's defaults, could maybe be a firmware bug. I'm assuming it's quite a new laptop given it has a 40-series nVidia GPU.
Best option: Wipe Windows, forget dual-booting. On that rig, albeit a laptop, you shouldn't have too much bottleneck running it in a VM. Whether you consider your OEM installation "license" transferable is between you and your maker, personally I do, but that may not be congruent with the law.
PS: Please remove the formatting on your post, it's literally making me dizzy. This forum doesn't support certain BBCode, but your color tags don't look right for anything. Protip:
[ COLOR=rgb(0, 0, 0) ] [ /COLOR ] (sans spaces).
Font size: 15, use bold, italics, or underline for emphasis.