I cannot connect to my tv from my phone via Chromecast built-in, either on YouTube or on the app Android tv remote. Both devices are on the same wifi network but the phone can't find the TV when searching. I tried uninstalling & then reinstalling the Chromecast & Android Webview apps on the TV, same on the phone but it didn't help. I suspect my wifi network to be the problem. Is there anything I can change in the router settings. Thanks.
I would try factory resetting the device and then setting it up using the Google Home App on your phone.
Edit: I think this won't work for integrated TV systems, unless they can be set up through the phone, I was thinking of standalone Chromecasts and standalone Android TV devices like the Mi Box, Shield etc.
This is more common than it should be. Here's the solution. On your TV: Settings->Apps->See All Apps->Show system apps->Chromecast built-in, then Clear data
Which TV?
On the router side, make sure client/AP isolation is disabled. Some routers may not have this however. Which router is it and is it provided by your internet provider?