Due to new Android requirements, the GrooveMixer application can no longer access the device's storage. Google doesn't allow access to the storage if the app is not a file manager, so it is impossible to update the app in the PlayStore! So the default app folder was changed.
ALL your old files are not deleted!
To add old grooves to the app, click Import button and in the opened file manager select the "/groovemixer/songs" folder and pick the file you want to import.