I have a MacBook Pro and work with different external monitors. The monitors have a keyboard and a mouse attached. Frequently the MacBook does not recognize the USB devices in the display and the keyboard and mouse do not function. I have to reboot. Is there a way to reset the USB system without rebooting?
Same problem here, it happens with a thunderbolt Apple display, and a thunderbolt LG display, and it's sometimes fixed after connecting/reconnecting/changing USB ports for the keyboard. On the LG even that did not work, only a complete reboot. I'm googling now for a USB reset solution that does not reboot my Mac.
Found this tool here: http://v6download.touch-base.com/downloads/MacProber/USB_Prober_Mac_OS_X_10.7.3.zip. Still works on Sierra. I will keep this handy on my desktop in case it happens again.