Please try the following troubleshooting steps:

1. Confirm whether the connected USB-C port on your laptop supports DP Alt Mode. You can verify this by checking your laptop's user manual, contacting the seller, or visiting the manufacturer's website. If the port does not support DP Alt Mode, it will not support external display through the hub.

2. Update your laptop's graphics driver to ensure compatibility and optimal display performance.

3. Try using the hub with a different laptop that has a USB-C port supporting DP Alt Mode to determine whether the issue is device-specific.

4. Swap the current HDMI cable or monitor to see if the issue lies with the external display setup.

5. Disconnect the hub from your laptop and unplug all connected devices. Wait at least 5 minutes. Then, restart your laptop and reconnect the hub to see if the issue is resolved.