Please try the following troubleshooting steps:

1. Confirm if the connected USB-C port of your laptop supports DP Alt Mode (display output). To do this, please consult your laptop's user manual, contact the seller, or check the manufacturer's website. If it doesn't support it, we are afraid that you cannot get an external display through the dock.

2. Make sure that you have used the included USB C cable to connect to the laptop. Another cable may not be able to support display out and prevent the HDMI ports from working.

3. Update the graphic driver of your laptop to see if it helps

4. Try the device with a different laptop that has a C port and the C port supports DP Alt Mode.

5. Try the device with a different HDMI cable/monitor

6. Please try unplugging the dock from your computer and disconnecting all devices from the dock for at least 5 minutes. Afterward, reboot your laptop and reconnect the dock to see if this resolves the issue.