Please try the following troubleshooting steps:

1. Make sure your laptop's USB-C port supports DP Alt Mode (video output). Refer to your laptop's user manual, contact the manufacturer, or visit their official website. If the USB-C does not support DP Alt Mode, the hub will not be able to output to an external display.

2. Update your laptop's graphics driver to the latest version to ensure display compatibility.

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

4. Try a different HDMI cable or connect to a different external monitor to rule out a faulty cable or display.

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