Are you using enterprise login with oAuth2? We found a bug when using native dashboard app accessing enterprise login page within oAuth2. This will be addressed in native dashboard app's UC release.
We have just released the new version of Operations Dashboard, you can install the app from http://www.arcgis.com/opsdashboard/OperationsDashboard.application. Please let us know if you still see the problem with the new version of the app.