Same problem here on watchOS 10. When calling requestWhenInUseAuthorization (or any other version of it) nothing happens. There is no system-dialog popping up only the delegate complaining about Error Domain=kCLErrorDomain Code=1.
It must be something with the project setup though. I made a small sample app and there it is working.
I tried removing the setting my app to App is only available as a standalone watchOS app and then the popup appears. I don't want that setting though. I do have a companion app.
Edit:
I just discovered this message in the console app:
{
"msg":"#AuthPrompt #Warning Delaying authorization request placed while insufficiently in-use",
"ClientKeyPath":i<my-bundle-id>.watchkitapp:,
"requestType":0,
"inUseLevel":0
}