I have a brand new Lattitude 5590 that goes into sleep mode at various times. Sometimes it wakes up but more times than not it does not.  I touch the keypad and the back light comes on or I touch the power/sleep button and it lights up.  The only way to get it back on is to hold the sleep/power down for 5 seconds to force a reboot.  NOT COOL!!!  Has latest BIOS and drivers.  Running Win 10 pro 64 bit.  If I put it into sleep mode with the button, it will not wake up either.