Not cleaning

When I try to use the app on my Samsung galaxy 8.4 it analyzes but the clean button doesn't work. It worked perfectly on my previous tablet,a Google Nexus. What can I do to make it work? I've tried reinstalling.

I have the same problem after just installing on my new RCA 7 Voyager tablet. Uninstalled and reinstalled. No difference. It is the version on Google Play today. v. 1.11.43. I still have over 4 GB space left in storage. I have KitKat 4.4. with a quad-core processor. Hope there is a simple solution. Thanks