Here are some steps to troubleshoot this issue:

1. Check connections and make sure all plugs are securely seated.
2. Make sure the external monitors are in the correct power and video mode.
3. Toggle the display options on the laptop (e.g. Fn + F5 or Menu button).
4. If possible, switch the cable or try plugging the external monitor into another device.
5. Ensure the device’s driver and firmware are up-to-date.