You might see this kind of message when data sync with Salesforce fails upon Check-In/Out.

Please sync the app with Salesforce by clicking the Sync with Salesforce button that is in the settings tab of the Mobile Time Tracker application.

Click the Menu button on the Mobile Time Tracker application, and click the settings button, and then click the "Sync with Salesforce" button. Then continue to use the app for tracking time in your org.