Having trouble starting a workout

I am having trouble starting a workout in watchOS 3 beta 1. I have requested authorization to all of my healthkit types and I have added the new iOS 10 plist info items (Privacy - Health Update Usage Description & Privacy - Health Share Usage Description). Here is what I am calling to start my workout:

    @IBAction func startWorkout() {
        let workoutConfiguration = HKWorkoutConfiguration()
        workoutConfiguration.activityType = .traditionalStrengthTraining
        workoutConfiguration.locationType = .indoor
  
        do {
            try self.workoutSession = HKWorkoutSession(configuration: workoutConfiguration)
            guard let workoutSession = self.workoutSession else { return }
            workoutSession.delegate = self
            self.healthStore.start(workoutSession)
        } catch {
            WKInterfaceDevice.current().play(.failure)
        }
    }

    func workoutSession(_ workoutSession: HKWorkoutSession, didFailWithError error: NSError) {
        WKInterfaceDevice.current().play(.failure)
    }

The delegate method workoutSession:didFailWithError end up getting called with the following error:

Error Domain=com.apple.healthkit Code=3 "Cannot start workout session while process is in background." UserInfo={NSLocalizedDescription=Cannot start workout session while process is in background.}

The app is in the foreground, and the workout was started directly from a UI button tap (I verified it is being called on the main thread). Does anyone have any ideas about what might be causing this issue?