Any chance that you have a eco or power save mode enabled on your TV? If yes, try disabling that mode to see if it makes wake on cast available.

That can result in the devices (TV in your case) turning the WiFi off, when the TV is powered down.

It could also be called quick or fast start mode, which should be enabled in that case.

Other than those things, you could also try disabling the wake on Lan on the TV to see if that enables the wake on cast. I think I read something about that somewhere in the past. In this case you might have to fiddle/mess with the TV settings.

Normally, the device connected (Android TV box, Roku, Fire devices for example) uses HDMI CEC to send commands to the TV it's connected to, but when the TV and the Android TV device are integrated, or is powered by the TV's HDMI or USB port, the TV going into a deep sleep or shutdown state can cause issues since the low power standby or shutdown mode may result in power not being sent to the ports or the internal device.

Check the TV's CEC settings and if it is not "on" or is set to "ARC only" that may be what keeps the TV from powering up in cast.

If the TV has a "one touch" power on mode, enabling that too may help/work, because the "one touch" would normally be a part of an external streaming devices HDMI CEC settings, and not necessarily the TV's.

In the end, it could be one of the things I mentioned, or something else I have not run into or heard about.

I do hope that you found this info to be useful/helpful.

Best of luck going forward!