Apple Fitness and Samsung Tv

I’ve had Apple devices since iphone3 came out. Having a love hate relationship with them lately. Just want to join up for Apple fitness and it won’t work on my tv even mirroring. You can see that it is possible to work cause you can see the preview. I tried the free three month fitness app and it looks amazing and really want to sign up but it won’t play with my tv. I even have an Apple TV 4K which can’t be read. I contacted Apple support and they ended up replacing the Apple TV but it still won’t read it. Not sure what I’m doing wrong in fact can’t see why it could possibly not work.