Please do try these troubleshooting steps that may help.
- First is to uninstall/reinstall the Sound card driver.
- Go to Device Manager and uninstall the Sound card driver.
- Once uninstalled, download and install the latest driver.
- Here's the link: https/download.lenovo.com/consumer/mobiles/audio121w7.exe
- Reboot the laptop once the latest driver has been installed.
- After the reboot, do make sure that the TV is set as the default Playback Device.
- Right click on the speaker icon and select Playback Devices.
- If the TV is now listed, right click on it and select Set Default then click Apply and OK.
If the same problem will persist, do a clean install of the graphics card driver.