DIAGNOSIS The USB hub in the monitor is powered and controlled by the upstream USB-B connection from your computer. An OS or driver update likely reset your USB power management settings or the hub driver itself.
FIX Let's retrace the physical connections first. 1) Ensure the square-shaped USB-B cable (the one that came with the monitor) is firmly connected from the monitor's 'USB Upstream' port to a working USB port on your computer. 2) The monitor must be powered on for the hub to work. 3) Check the OSD: Press the joystick, go to the 'System Setup' menu (the wrench icon), then 'USB Hub'. Make sure it's set to 'On'. Now, on your Windows PC, go to Device Manager. Look under 'Universal Serial Bus controllers'. Right-click and 'Scan for hardware changes'. If you see an 'Unknown device' or a device with a yellow warning, right-click it and select 'Update driver', then 'Search automatically for drivers'.
IF THAT DIDN'T WORK You may need to manually reset the USB hub power. Unplug the USB-B cable from your computer, then unplug the monitor's power cord from the wall. Wait 60 seconds. Plug the monitor power back in, let it boot, then reconnect the USB-B cable to your PC. This performs a cold restart of the hub.
HEADS UP The USB hub shares bandwidth. If you're connecting high-bandwidth devices like external SSDs or multiple webcams, try using fewer ports or connect those demanding devices directly to your computer to avoid overloading the hub.