Hello! I'm Jen, and I'd be happy to help you out with this issue.
I'm sorry to hear you're experiencing this issue. Is it a wired or a wireless connection? If your PC is connected to the TV with a cable, press Windows key + P to open Windows presentation mode and select Duplicate. If it's wireless, press Windows key + P then click 'Connect to a wireless display' and select your LG TV from the list. Make sure your laptop has a wireless LAN card for wireless display. You may check the following article for more information.
https://www.lg.com/us/support/help-library/lg-t...
https://www.lg.com/us/support/help-library/lg-t...
Note: These are non-Microsoft websites. The pages appear to be providing accurate, safe information. Watch out for ads on the site that may advertise products frequently classified as a PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the site before you decide to download and install it.
Let me know if this solution works for you. If not, please feel free to reply, and I'll be happy to provide further assistance. Thank you.
Best Regards!
Jen :)