Here are some things that you can try to get your computer to recognize your new external monitor:

1. Check connection cables to ensure they are properly connected to the device and the computer.
2. Ensure that the external monitor is compatible with your computer’s video output port by referring to the product specifications.
3. Check the power connection to ensure that the external monitor is receiving power.
4. Restart the computer and check under your video settings if the external monitor is listed.
5. Check the external monitor manufacturer website for any updated drivers or software for the product.