Windows 10 reverted a setting to disable sleep/wake timers in the OS
Check the advanced power options
Control Panel\All Control Panel Items\Power Options or
Winkey+R > powercfg.cpl
CLI: powercfg (note options
Windows 10 caused a bug to be highlighted in a device driver
Industry specifications work as a guide so (hopefully) all pieces work together. Sometimes people make mistakes, are lazy, or are ignorant and things break. Microsoft may appear at fault when they really are not.
Check the manufacturer's website of your PC's hardware for updated drivers.
Windows 10 updated an existing driver that has a bug in it
Likely driver culprits that would affect this behavior could be:
- Video graphics driver
- Intel management Engine Interface (EMI) driver
Try upgrading/downgrading/reinstalling them.
Windows 10 has a bug in it
A day after Windows 10 Tech Preview was released in 2014, Microsoft released kb3010668 to deal with power/sleep issues so check for MS updates.
A device may be attached to the PC that is preventing the sleep/wake timers
Could be something like a printer left on or something else seemingly trivial like that.
You forgot you had modified the BIOS/UEFI to save money on electricity by turning off the wake timers without realizing they were related to the wake timers in task scheduler...
You could always try resetting the BIOS settings.
If all else fails....