Hi supersystem1121, Please try the below mentioned steps: Check if the above steps work and reply.
Computer will not fall asleep by itself. Windows 8 Professional 64 Bit is the OS.  Sleep Settings = Sleep after 10 minutes.   USB Selective Suspend = Enabled.    Hard Disk Sleep = 9 Minutes.    Wake Timers are Disabled.   We have suspended all suspect Applications and still the Computer will not Sleep.    If you have any suggestions they would be appreciated.
XPS 8500 will not Sleep automatically