optiplex 9020 sff won't wake up with mouse or keyboard

Your computer is automatically hibernating since that is the default setting after a length of time sleeping. It requires a brief press of the power button to wake it. It looks like it is rebooting but all your open files and programs will still appear. You can disable it if you want by opening Power Options, Advance power settings, change your power plan.

Don't mess with bios on a new computer.

Hi @cmacra,

Once I switched my 755 from Win7 and Win10, it won't wake at all from sleep mode with mouse or keyboard.  Before, Sleep button on keyboard would wake it.  Now, I simply have to use the power button instead.

Make sure hibernate is off in your Power Options.

Did you check Power Management settings in BIOS?

Thanks.  Further info might help clarify the problem: 

I am running Windows 10 with USB wireless keyboard and mouse and AOC monitor via DVI. I have left the PC running the bios rather than uefi mode. Latest bios is loaded, all driver are up to date and of course latest Windows 10 is running with power saver options and other sleep settings the same as other pc's in our house. Problem is that for short term sleep periods the monitor or keyboard do wake up the pc and display, however for longer periods like overnight, movement on mouse or keyboard do not wake up the screen even though the PC shows it is no longer in sleep mode (indicated by constant power light state). I have tried two monitor brands and two different brand wireless keyboards and it makes no difference. I have tried factory settings for bios and tested (no change) and then disabled deep sleep, and enabled usb wake support in bios, and the problem persists. (The monitors and keyboard mouse combos work fine on other PCs). 

Thanbks for that.  When the power button is pulsing it sometimes brings the entire system to wake state but also sometimes decides to reset.  I've tried some changes to power plan but would be interested in what you have set in yours, as mine is set to the same as other pcs in the house and they work fine.

@cmacra 

In your bios, what are the processor C-States set to?

Not sure what to tell you about C States!  in Performance section of BIOS C State control is enabled by default and Limit CPUID Value is not enabled.

Mine is set for max performance.  Nothing shuts off by itself, other than going to screensaver.

You know the option "When I press the power button..."?  Mine is set to sleep.  Power button still wakes it up from sleep or off modes.

I'm with @bradthetechnut on this one. I have never liked Hibernate. 

I don't mind the cpu going into low power C states, but even some of those are a pain. I am thinking of Intel's 6th gen cpu's going into S6-S9 sleep states. I would disable those, but that's not a problem on the 9020 Haswell generation.

I would also update your BIOS to the latest Rev, it might weed out some issues.

@cmacra 

Try this:

1. Disable C states in the bios. Boot into windows as usual, and then go to your power settings:
2. Control panel/power options: Click 'change plan settings' for whichever plan is currently selected (.eg. balanced). Click 'change advanced power settings'.
3. You'll see a list of many options. Look through these and decide if they make sense or what to do with each one.
4. Especially look at the settings for usb and make sure USB is not allowed to power off or suspend.
5. Disable anything regarding hibernate or 'allow hybrid sleep'. This microsoft obfuscation is actually hibernate (write to disk). You can keep regular sleep settings and you should, in order to test out the system.

OK or yes your way back out so any changes are saved.

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Go back into control panel/ power options. Click 'choose what the power buttons do'. Click 'change settings that are currently unavailable'. Deselect 'turn on fast startup'.

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NOTE: Write down, and keep track of what you have changed!

For good measure, reboot. It's a very old microsoft tradition

Now try testing it out again. If it works OK, you can go back into control panel and re-enable any options you would like to keep. Do this one thing at a time, so you will eventually find the one that is the culprit.

As @CharlesIsWorking  suggested, a bios update could fix the problem too. You'll have to decide if you want to do that first. As @Mary G  suggested, I generally don't take the risk unless I know it is definitely an update which addresses the specific problem. Sometimes it's hard to know, what with dell's vague and notorious secrecy.

Good luck, and please let us know how it goes.

Thanks again.  I'll try following your suggestions.  However, it may take a day to check each change out given that sometimes I need to wait overnight for the problem to occur.

Yep, it will certainly take some time to check.  I think most here would like to hear what happens.

But it could help someone else down the line. Thanks for sticking with it.

I think donm4599x's suggestion to change the USB selective suspend setting to Disabled in the Plugged in section is probably the right solution. I once had the same issue and that's what fixed it for me.

I 3rd that.  My USB selective suspend is off also.  I rarely have to think about it.

Thanks I disabled USB Selective Suspend three days ago and it made no difference.  I'm trying a few other things and will report back.  It just takes a day to get identify whether a change made any difference to the problem.to the point of the problem