Can someone please explain how can I download the Activity app?

I have an Apple Watch series 5 and when I start pairing it with my iPhone X it says that it will download the "Activity App" to my iPhone but it doesn't!! When I search the app in Safari, it says "This app requires specific features not available on this device." I have unpaired and paired my watch and phone again but same story. I have tried turning my phone and watch off and back on as well as Hard Reset but it didn't help! Can someone please explain how can I download the Activity app???