There are several things you can check.
1. Make sure your device has been updated to the latest version of app.
2. Check to make sure you have uploaded a RMGC file and not a backup or GEDCOM file.
3. If there is some corruption in your RootsMagic database it may cause the app to not work with it. You will want to run File>Database Tools all options in consecutive order on your RootsMagic database prior to uploading the file to your device.