mac mini doesn't like USB keyboard & mouse

Why does my late 2014 mac mini disconnect the usb keyboard and usb mouse? It seems the mac mini only wants to connect Bluetooth devices. When waking up the computer from sleep mode, the keyboard and mouse are non-operable. I have to power off the mac mini manually with the power button, then reboot. The computer is connected by Ethernet to a router.



In System Preferences, Bluetooth is turned on - because it connects to a wireless printer. I notice that the Bluetooth preference pane keeps searching for a device, but none is listed. Although no printer shows in the Devices list, Printer Sharing is turned on and printing wirelessly is not a problem. I'm wondering if the printer was listed under Devices, perhaps Bluetooth would be happy and not mess with the usb connected keyboard and mouse.



Help would be appreciated because it's rather silly to have the computer go to sleep in 5 minutes, and still have to manually shut down and re-start the whole system just to use the keyboard and mouse.