@robaird I ran the terminal command "pmset -g assertions" and this is the result. I have highlighted in red what I think the problem is. Now I need to know how to fix it.
NetworkClientActive 0
InternalPreventSleep 1
Listed by owning process:
pid 48(powerd): [0x00002062000d8606] 00:00:13 InternalPreventSleep named: "com.apple.powermanagement.acwakelinger"
Timeout will fire in 31 secs Action=TimeoutActionRelease
pid 103(hidd): [0x00001de5000984d3] 00:11:03 UserIsActive named: "com.apple.iohideventsystem.queue.tickle.4294970828.11"
Timeout will fire in 1495 secs Action=TimeoutActionRelease
Kernel Assertions: 0xc=USB,BT-HID
id=530 level=255 0x4=USB mod=01/01/1970, 01:00 description=com.apple.usb.externaldevice.14800000 owner=HD Pro Webcam C920
id=531 level=255 0x4=USB mod=01/01/1970, 01:00 description=com.apple.usb.externaldevice.14b00000 owner=H115i
id=532 level=255 0x4=USB mod=01/01/1970, 01:00 description=com.apple.usb.externaldevice.14700000 owner=Dell AC511 USB SoundBar
id=533 level=255 0x4=USB mod=01/01/1970, 01:00 description=com.apple.usb.externaldevice.14e00000 owner=BRCM20702 Hub
id=535 level=255 0x8=BT-HID mod=01/01/1970, 01:00 description=com.apple.driver.IOBluetoothHIDDriver owner=AppleHSBluetoothDevice
id=536 level=255 0x8=BT-HID mod=01/01/1970, 01:00 description=com.apple.driver.IOBluetoothHIDDriver owner=AppleHSBluetoothDevice
Idle sleep preventers: IODisplayWrangler
Andrews-iMac: