Why my iOS app does not ask user permission to access camera?

I develop iOS app and it uses camera. AVCaptureDeviceInput is used to interface to camera. I checked Authorisation status as

- (void)checkDeviceAuthorizationStatus { 
    NSString *mediaType = AVMediaTypeVideo; 
    [AVCaptureDevice requestAccessForMediaType:mediaType completionHandler:^(BOOL granted) { 
     if (granted) { 
            [self setDeviceAuthorized:YES]; } 
       else { 
         dispatch_async(dispatch_get_main_queue(), ^{ [[[UIAlertView alloc] 
        initWithTitle:@"AVCam!" message:@"AVCam doesn't have permission to use Camera, please change privacy settings" 
       delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil] show]; 
       [self setDeviceAuthorized:NO]; 
    });
 } }]; }

When I launch the application, why it does not ask user permission for access to the camera? So the app does not appear in settings/privacy/camera to manually allow to access camera. Then show this error

"AVCam doesn't have permission to use Camera, please change privacy settings"

That means the app is not allowed to access the camera without asking user permission. Not only camera, camera-roll also has the same problem.

All these things happened after I reset settings in Settings/Reset/Rest All Settings. Before that the app was working well.