LG 42PG20D: 120hz TV not compatible with the 120hz update?

I am sorry to hear about your TV issue.

TruMotion is a trick that LG uses for smoothing motion, called frame interpretation, it is not a true 120Hz display. The HDMI inputs for this TV only support up to 60Hz.

You can learn more about it, and what all of the other TV manufacturers do here: https://www.cnet.com/news/fake-refresh-rates-is-your-tv-really-120hz/

To achive 4K at 120hz your TV needs to have HDMI 2.1 ports and supports 120hz, such as the LG CX TV,

The bandwidth limit of HDMI 2.0 will only allow 4K at 60hz.

Yeah I also have that and I have a Lg nanocell 866pa 4K 120hz tv

Thank you for your response, yes I understand your answer it’s down to the timings of the monitor that it work on the console. If I give you an example I’m currently looking at the LG UltraGear 27GP850-B. Am I right in saying this will be compatible at 1440p 120hz? Also the timings in the manual does it have to be exactly 120hz, I see some that are listed higher than 120hz but not 120hz exactly?

Yes, 60Hz is the standard in America. I think it's 50Hz for some European sets, but that might be historical. They might all be 60Hz now. Some modern TVs support 120Hz, like mine, the LG B7 OLED, which the Xbox One is also compatible with in some cases.