I'm having the same issue; the case being the computer isn't actually going to sleep, only the display is turning off because of inactivity. Moving the mouse or pressing a key is normally enough to turn the screen back on, but all it does is cause the keyboard backlight to turn on (which it wouldn't do were it actually asleep, as opposed to just having an unresponsive display).
@submarinescreendoor that sounds like the system hasn't been setup properly to enter sleep mode. Can you help me out with some additional troubleshooting details please -
a) Has this issue always been present or is it something that has only happened recently?
b) What version of Windows are you running?
c) Does the system enter sleep mode properly if you close the screen over or press the power button?
d) Are you running the latest BIOS and drivers on the system?
My suggestion would be to work through the steps outlined in this Non Dell article about sleep mode - https://windowsreport.com/computer-wont-go-sleep/
If you are still having problems after that I would recommend more in depth troubleshooting as per our article - https://www.dell.com/support/article/jm/en/jmbsdt1/sln309800/windows-10-troubleshooting-sleep-hibern...
I'll drop you a private message to get your service tag details.
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