I have a Xiaomi Mi TV 4A Pro 43 inch smart TV. It runs Android TV and came with Chromecast built-in. When I click the cast button on the Netflix app for iOS, I'm able to see my TV, but it always fails to connect. Can anyone help me out with this or if there's a way for me to install the TV version of Netflix on my Mi TV?
No there is no way. You can use a mobile app on your tv.
If your TV supports Widevine L1, you should give Kodi Netflix plugin a try first ( https://github.com/CastagnaIT/plugin.video.netflix ) before switching to Netflix mobile app. You can use "DRM Info" to find out if Widevine L1 is supported ( https://play.google.com/store/apps/details?id=com.androidfung.drminfo&hl=en_US ).
You can find more info here:
There shouldn't be the need for this after the Pie update. I just got Pie today on my 4A Pro 32, and aideloaded the Netflix For Android APK from APKMirror and it works flawlessly.
You might as well use modded version of Netflix instead of trying to cast from handphone. This is because MiTV is not certified by Netflix and it does not have level 1 DRM certification. Unlike the real ChromeCast, the ChromeCast built-in uses TV's CPU and processors and will not work if the TV itself cannot play Netflix.
https://skyjuiceiswater.blogspot.com/2019/04/playing-netflix-movies-in-xiaomi-tv4.html
https://skyjuiceiswater.blogspot.com/2019/09/differences-between-mirroring.html
The Mi TV aren't certified for Netflix (the app and casting).