beIN app won't cast from my android phone to the TV

turn off any VPN on the phone first. it either stops the phone finding the TV at all or the app sees a different country and refuses the stream.

Is the cast icon missing completely, or does it connect and then just show a black screen? Missing icon is usually the network: phone and TV/Chromecast have to be on the same Wi-Fi, and a lot of routers put the 5GHz and 2.4GHz bands or a guest network on separate segments so they can't see each other. Updating the app and the Google Home app helps more often than you'd think too. Black screen with sound (or nothing) is different. That tends to be rights protection, and some events just aren't allowed to go to a TV that way. Screen mirroring the whole phone hits the same wall because the stream is protected. If that's what you're seeing, an app on the TV itself or a streaming stick with the app installed is the way round it.