Hdmi-Cecil/simplink not working on lg tv

deactivate the simplink option on you lg tv and it will perfectly work. just done it!

Have you checked the TV itself?

I have an LG TV (different model) and sometimes HDMI-CEC is disabled on my Xbox One X's HDMI input after I change audio output (if I want to use my headphones for a while, for example). Its weird, I've never been able to get to the bottom of why
it happens but, sure enough, go to my TV's general settings while on the HDMI input and SIMPLINK (LG's name for HDMI-CEC) is off. Turn it back on and I'm good to go.

- Jason

No Simplink option on the TV

I will try a HDMI switch in a few days hopefully it will isolate the signal

There should be the "Auto Sensing" option that allows the management of the devices connected to the TV through SIMPLINK.
It can also depend on a faulty HDMI cable. Have you tried to replace it?

LG's HDMI support is notoriously unstable, not sure if it is the way they handshake or whether their software is poor but it is a long standing complaint you can find in many places on the internet.

Xbox 360 had issues with LG TV's as well (do a web search for xbox one lg tv hdmi and you'll get pages of results including PlayStation issues connecting to LG TV's so not limited to Microsoft).

Things to try:

On your TV that it works with, set your Xbox One to a lower resolution i.e. 720p then plug it in to the LG TV and see if it works.

Check for a TV firmware update

Reset TV to factory default settings

Try other HDMI cables

Try a HDMI to AV converter for your sister's TV and use AV cables with your Xbox One when using that TV.