My 2008 iMac/10.10.5 has recently refused to sleep... either automatically or with a menu command.
The internal HD failed some time ago, since which it's been running fine on an external usb hd.
No 'sharing' options are enabled. 'Wake for network access' is not enabled. 'Allow Bluetooth devices to wake...' is not enabled. The issue also happens with a 'test' account.
SMC and NVRAM have been reset.
'pmset sleepnow', 'osascript -e 'tell application "System Events" to sleep'' and 'osascript -e 'tell application "Finder" to sleep'' immediately sleep the display but not the system.
The 'energy pane' of Activity Monitor doesn't show any apps preventing sleep.
I'd had an issue with 'addressbooksourcesync' preventing sleep, but think that's now sorted.
'pmset -g assertions' shows '0' for 'PreventUserIdleDisplaySleep' and 'PreventUserIdleSystemSleep'.
Assertion status system-wide: BackgroundTask 0 ApplePushServiceTask 0 UserIsActive 1 PreventUserIdleDisplaySleep 0 PreventSystemSleep 0 ExternalMedia 1 PreventUserIdleSystemSleep 0 NetworkClientActive 1 Listed by owning process: pid 195(cupsd): [0x0000004600110135] 00:10:00 NetworkClientActive named: "org.cups.cupsd" pid 49(powerd): [0x0000003c0008012c] 00:10:11 ExternalMedia named: "com.apple.powermanagement.externalmediamounted" pid 95(hidd): [0x000000a500090183] 00:08:25 UserIsActive named: "com.apple.iohideventsystem.queue.tickle" Timeout will fire in 218 secs Action=TimeoutActionRelease Kernel Assertions: 0xc=USB,BT-HID id=500 level=255 0x4=USB mod=21/12/2016 12:46 description=EHC2 owner=AppleUSBEHCI id=501 level=255 0x4=USB mod=21/12/2016 12:46 description=EHC1 owner=AppleUSBEHCI id=503 level=255 0x4=USB mod=21/12/2016 12:52 description=UHC4 owner=AppleUSBUHCI id=506 level=255 0x4=USB mod=21/12/2016 12:55 description=UHC3 owner=AppleUSBUHCI id=507 level=255 0x8=BT-HID mod=01/01/1970 01:00 description=com.apple.driver.IOBluetoothHIDDriver owner=BNBMouseDevice