Diagnosis
The USB hub is inactive. It requires both data and power from the upstream USB-B connection to your computer.
How to Fix It
Two cables are mandatory. 1. Ensure the monitor's included USB-B to USB-A cable is connected. The square USB-B end plugs into the port labeled 'USB IN' on the monitor. The standard USB-A end plugs into a USB port on your computer. 2. The monitor must be powered on via its AC adapter. The USB hub draws power from the monitor's internal supply, not from your PC. Once both connections are verified, the downstream USB ports will be active.
If That Didn't Work
The specific USB port on your computer may not be providing sufficient power or data. Try a different USB port on your PC, preferably a USB 3.0 (blue plastic) port. Also, check your computer's Device Manager for any issues with 'Generic USB Hub'.
Heads Up
These are USB 3.2 Gen 1 (USB 3.0) ports. They provide up to 5V/0.9A (4.5W) per port. This is sufficient for data peripherals and slow phone charging, but not for fast-charging modern smartphones.