Please try the following troubleshooting steps:

1. Confirm if the connected USB-C port on your laptop supports DisplayPort Alt Mode (display output). Consult your laptop's user manual, contact the seller, or check the manufacturer's website. If it doesn't support DisplayPort Mode, the external display will not function.

2. Try the device with a different laptop that has a USB-C port supporting DisplayPort Alt Mode.

3. Make sure that you have used the included USB-C cable to connect to the laptop.

4. Unplug the KVM switch from your laptop and disconnect all devices for at least 5 minutes. Afterward, reboot your laptop and reconnect the KVM switch.