RPi 4B with LE12 CEC connection issue

If I turn on the TV before turnning on the RPi, everything works well, but not the other way around.

I've followed the procedure discribed in https://wiki.libreelec.tv/configuration/edid#generic-x86_64 and run "getedid create" successfully already.

Now the TV can be turned on when I switch on the RPi, which is my intention to run getedid. However it seems that the TV is on after the RPi is trying to connect to the CEC adaptor, so the connection can not be established. Is there a way to delay connecting CEC adaptor or to wait for the TV to be on before connecting CEC adaptor?

Quote from Da Flex

On your TV RC switch to TV mode, and then back to AV mode. Does that make CEC work?

No. It doesn't work this way. However if I turn off and then on the TV again, the CEC connection can be completed while the RPi stays on.

Quote from Da Flex

• click at Settings -> System -> Input -> Peripherals -> CEC Adapter
• enable "Switch source to this device on startup"

It's already enabled.