Joplin doesn't sync with "file system"

I use “file system” to sync my Android and desktop. I copy the notes files (xx… from the android memory card into the desktop sync directory.
Since I’ve updated Joplin, although all the files are in their place, Joplin does’t not show any notes. When I create a new note, a new file is created in the sync directory - Joplin knows the directory.
Why can not Joplin see my old notes?

Maybe some sync state still left in the app? Have you tried deleting the config directory and setting up sync again?

I deleted “.config/joplin-desktop/” and set up sync again.
now Joplin shows my notes.