Hi, Bench -
Thanks for your reply.
I tried all your suggestion. The only change made was #3 - powercfg -restoredefaultschemes (and then putting hibernate back in the shutdown menu).
Now when I set a timeout, the timeout does work and the machine hibernates when it should.
But the timeout still can't be set in the Advanced settings menu. I have to use powercfg /x hibernate-timeout-ac .
Any further ideas, or should we just declare success if not understanding?
BTW re #5: There is no Power troubleshooter under Settings > System > Troubleshoot > Other troubleshooters. Is it somewhere else? I am running Windows 11 Pro 24H2 OS build 26100.3775.