I had the problem for a few days that my mouse no longer woke up my computer. I looked in BIOS settings, and mouse settings, all was as it should be. But then I looked into what updates I had installed, and on the same day I updated "Intel(R) Network Connections" was when the mouse problem started. So I just uninstalled that, and now the mouse wakes up computer.
I just tested some tweaked settings through device manager as suggested. I realized it's not the buttons, but the mouse sensor that doesn't wake the one computer. So even if the mouse is set to wake the computer it won't awake by strictly mouse movement, only button presses.
Not sure why, as the other computer wakes up from mouse movement. Probably just a sensor specific thing. Not a big deal either way, just thought I'd share.