Unable to AirPlay Safari's streaming videos to Apple TV 4K fullscreen connected to HDTVs...

Hello.

I'm having problems AirPlaying streaming videos from two ATV 4Ks (A1842 & MQD22LL/A; 5th gen.) to HDTVs from two different Apple devices' Safari web browser with https://www.olevod.com's streaming Chinese videos.

1. An over year old Intel 13" MBP's: Its mirrored desktop mode works so I can see both screens. However, I can't get Safari's the streaming videos to show up fullscreen on HDTV via ATV 4K. I never see their AirPlaying stream videos.

2. Jan. 2015 iPad air (ME993LL/B; A1475; 1st gen. model; iOS v12.5.5, 16 GB): It seems to get stuck showing its ads in loop and not its movies.

This Chinese web site doesn't have an iOS app so I have to use the web browsers (Chrome doesn't even have an AirPlay option like in Safari). YouTube had no problems to AirPlay from Safari.

Am I missing something? All softwares have the (new/lat)est updates. I had to use MBP's mirror desktop and tell web browser's embedded video player to go fullscreen. :(

Thank you for reading and hopefully answering soon. :)