Please try the following troubleshooting steps:

1. Confirm whether the USB-C port on your laptop supports DP Alt Mode (video output). Refer to your laptop's user manual, contact the manufacturer, or check the official website. If the port does not support DP Alt Mode, the hub cannot output video to an external display.

2. Update your laptop's graphics driver to the latest version. This may resolve compatibility issues affecting external displays.

3. Try the hub with a different laptop that has a USB-C port confirmed to support DP Alt Mode.

4. Use a different HDMI cable or try connecting to another monitor to rule out hardware issues.

5. Unplug the hub from your laptop and disconnect all connected devices. Wait at least 5 minutes, then reboot your laptop and reconnect the hub to see if the issue is resolved.