Hi,
I had a similar issue lately, and after a few hours searching, I had found something really easy to do.
You open
cmd (Admin) or
Powershell (Admin), then you type «
powerconfig.exe /hibernate on »,and press “Enter”.
You close the command prompt, and it should be working, no need to reboot.
For unknown reason my “hibernate” was switched off after a cumulative update !???
Keep us informed !