I use this program to check what is keeping my computer from going to sleep and also to keep it from going to sleep while downloading.
Coffee
http://sourceforge.net/projects/coffee-sc/Features
Prevents standby when Downloading
Prevents standby when transfering files over the network
Prevents standby when using web installers
Provides insight into why your computer wont enter sleep
Saves you having to change the power setings to never and back again all the time
Saves you from having to redownload a file that will not resume after sleep
more to come....
It will show what applications or devices are keeping your system from sleeping.
For instance if I have teamspeak open using my wireless USB headset it prevents sleep. This app states something like: /dev/Logitech USB audio stream.
Anyways this function is in extra's then sleep blockers in the application. If nothing is showing up in here then I woud start looking at hardware or bios settings.
-Desktop-
Asus Crosshair VIII Dark Hero / AMD 5800x / 32GB Corsair Dominator Platinum RBG (CMT32GX4M4C3600C18) @ 3800 /2x Sabrent 1TB Rocket NVMe 4.0 (Raid 0)/ 1x Samsung 860 Evo SSD / Corsair AX1200 PSU / ASUS Strix Helios Case / Corsair HydroX Custom Loop D5, CX7, XG7 420+280 Rad/ Asus Strix 3090 / Asus PG35VQ Ultrawide Monitor / Corsair Commander PRO 3x ql120, 4x ql140 fans / Edifier 1850DB Speakers + T5 Sub /
Asus Theta 7.1 Headset