Thanks for using our forums. Sorry to hear you are having issues with the Android tablet. We did have a few reports of people getting this same issue, but everything should be resolved now. Are you still having this issue? If so, uninstalling and reinstalling the app should work. You may want to try that step again. The article below should help you further. It does state that it is for Android phones, however, the directions for the tablet are the same.
The Sling Moderation Team