Way I can’t use walkie talkie or download it on my Apple Watch series 4?

I have the series 4, and somehow I can’t download the walkie talkie app from my AppStore on my watch.

my brother have the 6 series and have it, so I know it work on my country. (Also the FaceTime works really good)

mom App Store on my watch it’s said “requires iPhone”

what should I do?

thanks!