I've had a similar issue where the power light stays on regardless of whether I try to Sleep from the Start Menu or hit Fn+F1. When the symptoms first started, laptop would just shut it's screen off and power button would stay lit indefinitely (plugged in) but I couldn't wake the machine up - only hold the power down for 5 seconds to hard shut down. I've reinstalled Windows 10 at least 6 times now. Sleep worked immediately in the beginning, but there may be some Windows/Driver update which automatically installs (since it's Win 10) that may contribute to this behavior (I suspected the Asus ATK driver, then the Asus Touchpad driver at one point, but wasn't able to really narrow it down consistently which was frustrating). Now, I have noticed that if I put the laptop into Airplane mode first, it will finally sleep 14 seconds later. If I try to to make it go to sleep otherwise, the screen turns off, power button light stays on perhaps indefinitely (laptop is still on since I can get sound effects with certain key strokes sometimes), but if I hit Fn+F1 even after the screen shuts off, it will go to sleep around 14 seconds later.
I've regressed some of the updates, used the "wushowhide.diagcab" method, set wi-fi to metered connection to try to avoid whichever update is causing this, with not much success - i thought I had it figured out since sleep was working immediately multiple times in a row, but then an update started installing in the background again and despite uninstalling and preventing new updates, I am still at the 14 second sleep thing again which is frustrating and confusing due to the inconsistencies.