I have a Panasonic TV and CEC is fine on a Pi4.
Usually when there is a problem with CEC, you should disconnect all HDMI devices from the TV.
Unplug from mains for a few minutes. Power on TV and connect just the Pi4 through hdmi and power it on.
See if that simple setup works. If it does gradually connect other HDMI cables and check if any cause an issue.
If the simple case doesn't work, I'd be suspicious of the hdmi cable. Some cheaper cables don't actually wire up the CEC lines (or they could be faulty).
Also not all HDMI sockets on TV are the same. There may be some (perhaps labelled PC) that don't support CEC. Test with same socket that you've seen working on a Pi0.
Do you have more than one device supporting CEC to your TV?
Try removing them all and only connect the RPi4.
My 2012 LG TV sometimes gets confused with multiple CEC connections at the same time.
Thanks for the advices, I tried this on all my TVs, did not work. Actually on my main TV I did not get any video signal 
(only audio) (never happened this before) (what I had before is color artifacts on HDMI1 input on TV, on HDMI2 it's ok, but only at fresh install...interesting)
The cable I'm using is an official Pi 4 HDMI/Micro HDMI cable.
I tried with the Pi Zero (I have raspberry OS lite on it for pihole, but I added kodi as well) Works straightaway, boom.
