The symptom is that you will see the "The app needs storage read/write access to unpack and access song packages." message on game start.
This applies only for Android 6 and higher.
The permissions are required in order for the game to unpack the smzip files as well as read the level data (Song/Banner/SM/DWI file e.t.c.) which are stored by default on your primary storage (Folder BeatX)
FIX: Just go to Android Settings/Apps/BeatX/Permissions and enable "Storage"