We are currently aware of an issue with apps reading data from the external storage under the Android 6 operating system.
This is due to Google's new adaptive storage feature, where rather than the Android device having the traditional internal and external storage locations, the storage is combined into 1 adaptive storage location.
This of course causes problems for apps which are coded to read data from both internal and external storage.
The quickest and easiest way to rectify this is for the Memory-Map app to re-create its 'map folders' data file. To do this all you need to do is uninstall and then reinstall the app using the Google Play Store.
If this does not work (as some Android devices restrict SD card access for apps), then you can manually force the Memory-Map app to create the 'map folders' data file. To do this download and install a File Manager app from the Google Play Store such as ASTRO File Manager or ES File Explorer and then use that app to manually navigate to where the maps are stored. Tap on a QCT file and you will be prompted to open the file with Memory-Map.