Walkie-talkie not working
Walkie-talkie app was not working due to a privacy related bug, so Apple disabled it. They resolved the issue in watchOS 5.3 which one would suspect will have the code present in the next watchOS 6 beta whenever it is released. At the moment you require watchOS 5.3 for the app to work.
This feature now works with watchOS 6 beta 5.