Hi,
Once the TV is connected to your laptop via HDMI, press the Windows key + P at the same time then select Extended Display then press Enter. If it will still not work make sure that your TV source is correctly set to the correct HDMI port. And if it will still not work, do uninstall/reinstall the graphics card driver.
- Go to Device Manager and uninstall the graphics card driver.
- Next is to open Programs and Features then uninstall anything related to the graphics card.
- Once done, download and install the latest driver from the manufacturer site.
- Reboot the laptop once the latest driver has been installed then test it again.
- If all these will not work do also try a different HDMI cable.