mid-2010 Mac Pro has stopped sleeping

Replacing the CMOS coin battery fixed the sleep problem!

The machine now sleeps just fine, both by Sleep preset and manually.

Thank you, HWTech!!!!

The old battery tested at 3 volts on an electronic multimeter. That type of tester doesn't load the battery, and therefore won't detect even drastic voltage drops when loaded. The same battery tested as just about worn out on a mechanical battery tester that uses battery voltage to move its needle, and thus can detect voltage drops on load. The new battery tested good.

Tips for anyone else who does this fix:

1. You must remove the video card in order to get to the coin battery. There are online videos that show you how to do this. The procedure varies a bit based on whether you have the stock graphics card or a replacement card.
2. The battery sits in a shallow indent with plastic nubs around it, and is held in by a stiff spring clip. This clip is NOT designed to fold away from the battery and motherboard, and will break if you try. Instead, slide the battery out sideways. I used my left forefinger to push on the left side of the battery next to where the clip attaches, and my right forefinger to lift the right side of the battery just enough to clear the nubs so it would slide.
3. Buy a new battery with a distant expiration date. I bought a good brand since it will be in my Mac for years and is a hassle to replace.
4. My battery came with plastic stuck to one side to protect the contact. Remove that.
5. Insert the battery by sliding it under the edge of the clip from the right side. Lever the clip up as little as possible. Push the battery in until it seats between the nubs. The labeled side of the battery with the model code faces you.

Clarifications:

The DISPLAY goes to sleep, but the Mac itself does not: the fans stay on, I sometimes hear disk reads, and the light on the front of the tower stays on rather than cycling on and off as it should in Sleep mode.

The problem happens whether or not the machine is connected to a network.

The machine is not hooked up to, or sharing, a printer or scanner. It usually has a non-networked external USB Time Machine backup drive attached.

Energy Saver is set to turn the display off after 10 minutes of inactivity, and put the machine to sleep after 15 minutes. (I have tried various other settings and they also don't put the machine to sleep.) "Wake for network access" is turned off. Sharing is turned off except for Remote Login and Remote Management.

Activity Monitor's Energy tab flags nothing as preventing the machine from shutting down.

Thanks!

I do not have the "Power Nap" option.

Yes, the screen sleeps when I manually sleep the Mac, or if I leave it running beyond the sleep time I have set. However, the machine does not sleep. I can still hear fans, occasional disk reads, and the light stays on.

Tried so far:

SMC reset

PRAM reset

System logs: in my reply to Illaass below.

I'll have a look at that battery tomorrow. It is probably as old as the machine.

System log, Safe Mode, part 1:

default 21:45:00.948452 -0700 opendirectoryd getpwnam failed with result Not Found

error 21:45:01.617971 -0700 WindowServer [ERROR] - Unknown CGXDisplayDevice: 0x41dc9d00

error 21:45:01.619600 -0700 WindowServer [ERROR] - Unknown CGXDisplayDevice: 0x41dc9d00

default 21:45:01.632655 -0700 kernel DW forced idle for 1000ms by process 'kernel_task' from 4

default 21:45:01.633336 -0700 powerd rootDomain's user activity state:0

default 21:45:01.633729 -0700 powerd Display state: Off

default 21:45:01.634204 -0700 bluetoothd Received User Active Changed Notification (0)

default 21:45:01.634618 -0700 bluetoothd Received User Active Changed Notification (0)

default 21:45:01.635809 -0700 powerd Activity changes from 0x11 to 0x10. UseActiveState:0

default 21:45:01.639217 -0700 sharingd ScreenOn changed: on -> off

default 21:45:01.635894 -0700 powerd hidActive:1 displayOff:1 assertionActivityValid:0 now:0x38e hid_ts:0x1a2 assertion_ts:0x38d

error 21:45:01.645164 -0700 WindowServer [ERROR] - Unknown CGXDisplayDevice: 0x41dc9d00

error 21:45:01.648368 -0700 WindowServer [ERROR] - Unknown CGXDisplayDevice: 0x41dc9d00

default 21:45:01.648241 -0700 kernel RTC: getGMTTimeOfDay 1555994701

default 21:45:01.652125 -0700 ARDAgent event ref 0x0

default 21:45:01.652829 -0700 sharingd Screen state changed to off

default 21:45:01.653006 -0700 sharingd BLE NearbyAction scanner stop

default 21:45:01.653112 -0700 sharingd Screen state changed to off

default 21:45:01.653206 -0700 sharingd ScanEligible: yes -> no

default 21:45:01.653413 -0700 powerd Process hidd.139 Summary UserIsActive "com.apple.iohideventsystem.queue.tickle.4294968395.17" age:00:00:00 id:38654738441 [System: DeclUser NetAcc kCPU kDisp]

default 21:45:01.653281 -0700 sharingd Discovery stop (shouldn't scan)

default 21:45:01.653654 -0700 powerd Process cupsd.269 Summary NetworkClientActive "org.cups.cupsd" age:00:12:52 id:73014476804 [System: DeclUser NetAcc kCPU kDisp]

default 21:45:01.653962 -0700 sharingd TTF: Problem flags changed: 0x0 < >, AirPlay no

default 21:45:01.654210 -0700 sharingd Invalidating

default 21:45:01.654419 -0700 sharingd Nearby stop scanning: scan request of type 15, blob: <>, mask <>, active: 0, duplicates: 0, screen on: No Scan, screen off: No Scan, rssi: -90, peers: (

) scan mode: 0

default 21:45:01.657334 -0700 kernel IOConsoleUsers: time(1) 0->1555994706, lin 1, llk 1,

default 21:45:01.657375 -0700 kernel IOConsoleUsers: gIOScreenLockState 2, hs 0, bs 0, now 1555994701, sm 0x0

default 21:45:01.657057 -0700 identityservicesd Network state changed

default 21:45:01.657173 -0700 securityd system will sleep

default 21:45:01.657721 -0700 loginwindow -[FMDFMMManager isFMMEnabled] 0

default 21:45:01.657263 -0700 securityd 0x7ffee9dd6a50 will sleep

default 21:45:01.657145 -0700 identityservicesd Network state changed

default 21:45:01.657937 -0700 corebrightnessd Will Sleep

default 21:45:01.658426 -0700 bluetoothd System will sleep

default 21:45:01.658591 -0700 UserEventAgent [BTUserEventAgentController messageTracerEventDriven] systemPowerNotification

default 21:45:01.657222 -0700 identityservicesd Network state changed

default 21:45:01.658634 -0700 bluetoothd Stopping Scan For Sleep

default 21:45:01.658683 -0700 UserEventAgent [BTUserEventAgentController messageTracerEventDriven]

default 21:45:01.657301 -0700 identityservicesd Network state changed

default 21:45:01.659232 -0700 AirPlayUIAgent 2019-04-22 09:45:01.659165 PM BecomingInactive: NSWorkspaceWillSleepNotification

default 21:45:01.659792 -0700 AirPlayXPCHelper <<<< FigRoutingManager_macOS >>>> routingManager_endpointUIAgentEventCallback: UIAgent callback received deviceWillSleep

default 21:45:01.659024 -0700 bluetoothd Controller will sleep: sending CBCentralManagerStatePoweredOff

default 21:45:01.660327 -0700 powerd Received kIOMessageSystemWillSleep. UUID: 0344A39F-C4E6-4347-9E3A-D033D5E04D76

default 21:45:01.663145 -0700 SiriNCService Advertiser state changed to 2 from 0

default 21:45:01.657375 -0700 identityservicesd Network state changed

default 21:45:01.664827 -0700 apsd power management notification 0x19

default 21:45:01.665580 -0700 AirPlayXPCHelper Advertiser state changed to 2 from 0

default 21:45:01.663680 -0700 timed cmd,PmCallback,msg,0x19

default 21:45:01.665541 -0700 sharingd Invalidated

default 21:45:01.660798 -0700 powerd Entering DarkWake state due to 'Software Sleep pid=134'

default 21:45:01.664325 -0700 UserEventAgent [BTUserEventAgentController messageTracerEventDriven] PowerSource -2.000000 -2.000000

default 21:45:01.661611 -0700 rapportd Bluetooth peripheral manager state changed: PoweredOff

default 21:45:01.657454 -0700 identityservicesd Network state changed

default 21:45:01.664971 -0700 apsd <private>: prepareForDarkWake

default 21:45:01.660072 -0700 bluetoothd

default 21:45:01.665836 -0700 sharingd Invalidating

Thanks, lllaass! I forgot to check for a support page before posting.

I ran through the checklist and didn't spot any of the problems they mentioned. Any ideas what to try next?