Win 7 PC Suddenly Will Not Sleep

PC has always been set to sleep after 20 min. Display sleeps as
expected, but PC has suddenly stopped sleeping. No hardware/software
changes other than Windows Update. Cannot find a clue in MS Support. Any
suggestions?

Frank L. Thiel wrote:
PC has always been set to sleep after 20 min. Display sleeps as
expected, but PC has suddenly stopped sleeping. No hardware/software
changes other than Windows Update. Cannot find a clue in MS Support. Any
suggestions?

https://www.sevenforums.com/performa...ng-system.html

powercfg -energy -output %USERPROFILE%\Desktop\Energy_Report.html

If you don't specify the output location, the report ends up
in what looks like the current working directory.

I tried running that from an elevated (administrator) Command
Prompt. And because the test was done in a Windows 7 VM, it said:

"System firmware (BIOS) does not support S3"

So that's my sleep-blocker right there. Your sleep-blocker
won't be that one, unless you have some older hardware, and
the default in the BIOS was S1, instead of "S1 & S3".

And while there is another command, I'm not sure it has
any diagnostic value.

powercfg -devicequery s3_supported

That one lists lots of things that support S3 sleep, but it
won't tell you about critical (i.e. real hardware) ones
that are blocking sleep.

So my guess is, the energy report will have to do.

There are several possibilities for ACPI problems:

1) System tries to enter a state, crashes, and restarts.
Sometimes a shutdown, where the system won't stay shut
down, is actually a crash followed by an automatic reboot.

2) System tried to enter sleep, and a wake_armed device
immediately wakes it up again. A NIC set to "wake on carrier"
will wake in about 10 seconds or so. There are other values
for NIC waking which will stop that. I have two mice here,
and the Microsoft mouse will wake the computer if it
moves a couple micro-inches. So that mouse must be disabled
in Device Manager.

The powercfg "-lastwake" command may help with those.

3) System cannot enter the desired state, because a "blocker"
is present. (Use energy report.)

Those are some examples.

Paul