Писал ли нативные модули

// Android модуль
public class CameraModule extends ReactContextBaseJavaModule {
  @ReactMethod
  public void startCamera(Promise promise) {
    try {
      Activity activity = getCurrentActivity();
      Intent intent = new Intent(activity, CameraActivity.class);
      activity.startActivity(intent);
      promise.resolve(true);
    } catch (Exception e) {
      promise.reject("CAMERA_ERROR", e.getMessage());
    }
  }
}

// iOS модуль
@objc(CameraModule)
class CameraModule: NSObject {
  @objc func startCamera(_ resolve: RCTPromiseResolveBlock, 
                        reject: RCTPromiseRejectBlock) {
    DispatchQueue.main.async {
      let vc = CameraViewController()
      UIApplication.shared.keyWindow?.rootViewController?.present(vc, animated: true)
      resolve(true)
    }
  }
}