I've just created (and activated) dev account in the sandbox environment. I've downloaded Clover: com.clover.engine-1455.apk and App Updater: com.clover.appupdater-1095.apk from sandbox.dev.clover.com/developers/dev-apks . I've installed them on Android tablet with 4.4.2 and on emulator with 4.4 and when I trie to log in I receive message An error occurred while communicating with the server. {"message":"Invalid credentials"}. My credentials are correct because I logged in successfully couple of times in sandbox.dev.clover.com. I also tried with this apk - docs.clover.com/wp-content/uploads/2015/09/com.clover.engine-1452.apk and same result.