title: iOS 12 - NSFaceIDUsageDescription all of a sudden not working
body: <p>I was using NSFaceIDUsageDescription in my app and it was working. I deleted my app from my device and and re-uploaded (plugging my device into my mac and running from xcode) it and now I don't get the alert that my app would like to use FaceID, how come the alert is not appearing anymore? This is preventing me from using FaceID in my app.</p>
  
  <pre><code>class TouchIDAuth {
  
      let context = LAContext()
  
      func canEvaluatePolicy() -&gt; Bool {
          return context.canEvaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, error: nil)
      }
  
      func authenticateUser(completion: @escaping (NSNumber?) -&gt; Void) {
  
          guard canEvaluatePolicy() else {
              completion(0)
              return
          }
  
          context.evaluatePolicy(.deviceOwnerAuthenticationWithBiometrics, localizedReason: "Logging in with Touch ID") { (success, evaluateError) in
                                  if success {
                                      DispatchQueue.main.async {
                                          completion(nil)
                                      }
                                  } else {
  
                                      let response: NSNumber
  
                                      switch evaluateError?._code {
                                      case Int(kLAErrorAuthenticationFailed):
                                          response = 2
                                      case Int(kLAErrorUserCancel):
                                          response = 3
                                      case Int(kLAErrorUserFallback):
                                          response = 4
                                      default:
                                          response = 1
                                      }
  
                                      completion(response)
  
                                  }
          }
      }
  
  }
  </code></pre>
  
  <p>And when I do this:</p>
  
  <pre><code>let touchMe = TouchIDAuth()
  print(touchMe.canEvaluatePolicy())
  </code></pre>
  
  <p>The print returns false.</p>
  
  <p>Is this an issue with my device? Or with NSFaceIDUsageDescription?</p>