I installed a windows 10 desktop recently which goes to sleep after a while if not used. The user reported that he left the computer there for a while and when he got back, simply pressing a key on the USB keyboard did not wake the computer up. He needed to press the power button.
I tested sleep when I was there it worked properly, I was able to wake the computer by pressing any key on the keyboard. ((I made it to sleep and woke it up right after that.)
Why is it that after a longer sleep the user could only wake the computer up with the power button, instead pressing a key on the keyboard?